diff --git a/index.js b/index.js
index 6c6be996..b5f4588d 100644
--- a/index.js
+++ b/index.js
@@ -623,20 +623,84 @@ function base64Slice (buf, start, end) {
 }
 
 function utf8Slice (buf, start, end) {
-  var res = ''
-  var tmp = ''
   end = Math.min(buf.length, end)
-
-  for (var i = start; i < end; i++) {
-    if (buf[i] <= 0x7F) {
-      res += decodeUtf8Char(tmp) + String.fromCharCode(buf[i])
-      tmp = ''
+  var firstByte
+  var secondByte
+  var thirdByte
+  var fourthByte
+  var bytesPerSequence
+  var tempCodePoint
+  var codePoint
+  var res = []
+  var i = start
+
+  for (; i < end; i += bytesPerSequence) {
+    firstByte = buf[i]
+    codePoint = 0xFFFD
+
+    if (firstByte > 0xEF) {
+      bytesPerSequence = 4
+    } else if (firstByte > 0xDF) {
+      bytesPerSequence = 3
+    } else if (firstByte > 0xBF) {
+      bytesPerSequence = 2
     } else {
-      tmp += '%' + buf[i].toString(16)
+      bytesPerSequence = 1
+    }
+
+    if (i + bytesPerSequence <= end) {
+      switch (bytesPerSequence) {
+        case 1:
+          if (firstByte < 0x80) {
+            codePoint = firstByte
+          }
+          break
+        case 2:
+          secondByte = buf[i + 1]
+          if ((secondByte & 0xC0) === 0x80) {
+            tempCodePoint = (firstByte & 0x1F) << 0x6 | (secondByte & 0x3F)
+            if (tempCodePoint > 0x7F) {
+              codePoint = tempCodePoint
+            }
+          }
+          break
+        case 3:
+          secondByte = buf[i + 1]
+          thirdByte = buf[i + 2]
+          if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80) {
+            tempCodePoint = (firstByte & 0xF) << 0xC | (secondByte & 0x3F) << 0x6 | (thirdByte & 0x3F)
+            if (tempCodePoint > 0x7FF && (tempCodePoint < 0xD800 || tempCodePoint > 0xDFFF)) {
+              codePoint = tempCodePoint
+            }
+          }
+          break
+        case 4:
+          secondByte = buf[i + 1]
+          thirdByte = buf[i + 2]
+          fourthByte = buf[i + 3]
+          if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80 && (fourthByte & 0xC0) === 0x80) {
+            tempCodePoint = (firstByte & 0xF) << 0x12 | (secondByte & 0x3F) << 0xC | (thirdByte & 0x3F) << 0x6 | (fourthByte & 0x3F)
+            if (tempCodePoint > 0xFFFF && tempCodePoint < 0x110000) {
+              codePoint = tempCodePoint
+            }
+          }
+      }
     }
+
+    if (codePoint === 0xFFFD) {
+      // we generated an invalid codePoint so make sure to only advance by 1 byte
+      bytesPerSequence = 1
+    } else if (codePoint > 0xFFFF) {
+      // encode to utf16 (surrogate pair dance)
+      codePoint -= 0x10000
+      res.push(codePoint >>> 10 & 0x3FF | 0xD800)
+      codePoint = 0xDC00 | codePoint & 0x3FF
+    }
+
+    res.push(codePoint)
   }
 
-  return res + decodeUtf8Char(tmp)
+  return String.fromCharCode.apply(String, res)
 }
 
 function asciiSlice (buf, start, end) {
@@ -1401,7 +1465,7 @@ function utf8ToBytes (string, units) {
         codePoint >> 0x6 & 0x3F | 0x80,
         codePoint & 0x3F | 0x80
       )
-    } else if (codePoint < 0x200000) {
+    } else if (codePoint < 0x110000) {
       if ((units -= 4) < 0) break
       bytes.push(
         codePoint >> 0x12 | 0xF0,
@@ -1453,11 +1517,3 @@ function blitBuffer (src, dst, offset, length) {
   }
   return i
 }
-
-function decodeUtf8Char (str) {
-  try {
-    return decodeURIComponent(str)
-  } catch (err) {
-    return String.fromCharCode(0xFFFD) // UTF 8 invalid char
-  }
-}
diff --git a/perf/readUtf8.js b/perf/readUtf8.js
new file mode 100644
index 00000000..a0109ff8
--- /dev/null
+++ b/perf/readUtf8.js
@@ -0,0 +1,19 @@
+var BrowserBuffer = require('../').Buffer // (this module)
+var util = require('./util')
+var suite = util.suite()
+
+// 256 random bytes
+var array = [ 152, 130, 206, 23, 243, 238, 197, 44, 27, 86, 208, 36, 163, 184, 164, 21, 94, 242, 178, 46, 25, 26, 253, 178, 72, 147, 207, 112, 236, 68, 179, 190, 29, 83, 239, 147, 125, 55, 143, 19, 157, 68, 157, 58, 212, 224, 150, 39, 128, 24, 94, 225, 120, 121, 75, 192, 112, 19, 184, 142, 203, 36, 43, 85, 26, 147, 227, 139, 242, 186, 57, 78, 11, 102, 136, 117, 180, 210, 241, 92, 3, 215, 54, 167, 249, 1, 44, 225, 146, 86, 2, 42, 68, 21, 47, 238, 204, 153, 216, 252, 183, 66, 222, 255, 15, 202, 16, 51, 134, 1, 17, 19, 209, 76, 238, 38, 76, 19, 7, 103, 249, 5, 107, 137, 64, 62, 170, 57, 16, 85, 179, 193, 97, 86, 166, 196, 36, 148, 138, 193, 210, 69, 187, 38, 242, 97, 195, 219, 252, 244, 38, 1, 197, 18, 31, 246, 53, 47, 134, 52, 105, 72, 43, 239, 128, 203, 73, 93, 199, 75, 222, 220, 166, 34, 63, 236, 11, 212, 76, 243, 171, 110, 78, 39, 205, 204, 6, 177, 233, 212, 243, 0, 33, 41, 122, 118, 92, 252, 0, 157, 108, 120, 70, 137, 100, 223, 243, 171, 232, 66, 126, 111, 142, 33, 3, 39, 117, 27, 107, 54, 1, 217, 227, 132, 13, 166, 3, 73, 53, 127, 225, 236, 134, 219, 98, 214, 125, 148, 24, 64, 142, 111, 231, 194, 42, 150, 185, 10, 182, 163, 244, 19, 4, 59, 135, 16 ]
+
+var browserBuffer = new BrowserBuffer(array)
+var nodeBuffer = new Buffer(array)
+
+suite
+  .add('BrowserBuffer#readUtf8', function () {
+    browserBuffer.toString()
+  })
+
+if (!process.browser) suite
+  .add('NodeBuffer#readUtf8', function () {
+    nodeBuffer.toString()
+  })
diff --git a/test/to-string.js b/test/to-string.js
index 172c9e90..8fd9db1f 100644
--- a/test/to-string.js
+++ b/test/to-string.js
@@ -115,3 +115,111 @@ test('utf8 to binary', function (t) {
   /* jshint +W100 */
   t.end()
 })
+
+test('utf8 replacement chars (1 byte sequence)', function (t) {
+  t.equal(
+    new B([ 0x80 ]).toString(),
+    '\uFFFD'
+  )
+  t.equal(
+    new B([ 0x7F ]).toString(),
+    '\u007F'
+  )
+  t.end()
+})
+
+test('utf8 replacement chars (2 byte sequences)', function (t) {
+  t.equal(
+    new B([ 0xC7 ]).toString(),
+    '\uFFFD'
+  )
+  t.equal(
+    new B([ 0xC7, 0xB1 ]).toString(),
+    '\u01F1'
+  )
+  t.equal(
+    new B([ 0xC0, 0xB1 ]).toString(),
+    '\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xC1, 0xB1 ]).toString(),
+    '\uFFFD\uFFFD'
+  )
+  t.end()
+})
+
+test('utf8 replacement chars (3 byte sequences)', function (t) {
+  t.equal(
+    new B([ 0xE0 ]).toString(),
+    '\uFFFD'
+  )
+  t.equal(
+    new B([ 0xE0, 0xAC ]).toString(),
+    '\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xE0, 0xAC, 0xB9 ]).toString(),
+    '\u0B39'
+  )
+  t.end()
+})
+
+test('utf8 replacement chars (4 byte sequences)', function (t) {
+  t.equal(
+    new B([ 0xF4 ]).toString(),
+    '\uFFFD'
+  )
+  t.equal(
+    new B([ 0xF4, 0x8F ]).toString(),
+    '\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xF4, 0x8F, 0x80 ]).toString(),
+    '\uFFFD\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xF4, 0x8F, 0x80, 0x84 ]).toString(),
+    '\uDBFC\uDC04'
+  )
+  t.equal(
+    new B([ 0xFF ]).toString(),
+    '\uFFFD'
+  )
+  t.equal(
+    new B([ 0xFF, 0x8F, 0x80, 0x84 ]).toString(),
+    '\uFFFD\uFFFD\uFFFD\uFFFD'
+  )
+  t.end()
+})
+
+test('utf8 replacement chars on 256 random bytes', function (t) {
+  t.equal(
+    new B([ 152, 130, 206, 23, 243, 238, 197, 44, 27, 86, 208, 36, 163, 184, 164, 21, 94, 242, 178, 46, 25, 26, 253, 178, 72, 147, 207, 112, 236, 68, 179, 190, 29, 83, 239, 147, 125, 55, 143, 19, 157, 68, 157, 58, 212, 224, 150, 39, 128, 24, 94, 225, 120, 121, 75, 192, 112, 19, 184, 142, 203, 36, 43, 85, 26, 147, 227, 139, 242, 186, 57, 78, 11, 102, 136, 117, 180, 210, 241, 92, 3, 215, 54, 167, 249, 1, 44, 225, 146, 86, 2, 42, 68, 21, 47, 238, 204, 153, 216, 252, 183, 66, 222, 255, 15, 202, 16, 51, 134, 1, 17, 19, 209, 76, 238, 38, 76, 19, 7, 103, 249, 5, 107, 137, 64, 62, 170, 57, 16, 85, 179, 193, 97, 86, 166, 196, 36, 148, 138, 193, 210, 69, 187, 38, 242, 97, 195, 219, 252, 244, 38, 1, 197, 18, 31, 246, 53, 47, 134, 52, 105, 72, 43, 239, 128, 203, 73, 93, 199, 75, 222, 220, 166, 34, 63, 236, 11, 212, 76, 243, 171, 110, 78, 39, 205, 204, 6, 177, 233, 212, 243, 0, 33, 41, 122, 118, 92, 252, 0, 157, 108, 120, 70, 137, 100, 223, 243, 171, 232, 66, 126, 111, 142, 33, 3, 39, 117, 27, 107, 54, 1, 217, 227, 132, 13, 166, 3, 73, 53, 127, 225, 236, 134, 219, 98, 214, 125, 148, 24, 64, 142, 111, 231, 194, 42, 150, 185, 10, 182, 163, 244, 19, 4, 59, 135, 16 ]).toString(),
+    '\uFFFD\uFFFD\uFFFD\u0017\uFFFD\uFFFD\uFFFD\u002C\u001B\u0056\uFFFD\u0024\uFFFD\uFFFD\uFFFD\u0015\u005E\uFFFD\uFFFD\u002E\u0019\u001A\uFFFD\uFFFD\u0048\uFFFD\uFFFD\u0070\uFFFD\u0044\uFFFD\uFFFD\u001D\u0053\uFFFD\uFFFD\u007D\u0037\uFFFD\u0013\uFFFD\u0044\uFFFD\u003A\uFFFD\uFFFD\uFFFD\u0027\uFFFD\u0018\u005E\uFFFD\u0078\u0079\u004B\uFFFD\u0070\u0013\uFFFD\uFFFD\uFFFD\u0024\u002B\u0055\u001A\uFFFD\uFFFD\uFFFD\uFFFD\uFFFD\u0039\u004E\u000B\u0066\uFFFD\u0075\uFFFD\uFFFD\uFFFD\u005C\u0003\uFFFD\u0036\uFFFD\uFFFD\u0001\u002C\uFFFD\uFFFD\u0056\u0002\u002A\u0044\u0015\u002F\uFFFD\u0319\uFFFD\uFFFD\uFFFD\u0042\uFFFD\uFFFD\u000F\uFFFD\u0010\u0033\uFFFD\u0001\u0011\u0013\uFFFD\u004C\uFFFD\u0026\u004C\u0013\u0007\u0067\uFFFD\u0005\u006B\uFFFD\u0040\u003E\uFFFD\u0039\u0010\u0055\uFFFD\uFFFD\u0061\u0056\uFFFD\uFFFD\u0024\uFFFD\uFFFD\uFFFD\uFFFD\u0045\uFFFD\u0026\uFFFD\u0061\uFFFD\uFFFD\uFFFD\uFFFD\u0026\u0001\uFFFD\u0012\u001F\uFFFD\u0035\u002F\uFFFD\u0034\u0069\u0048\u002B\uFFFD\uFFFD\uFFFD\u0049\u005D\uFFFD\u004B\uFFFD\u0726\u0022\u003F\uFFFD\u000B\uFFFD\u004C\uFFFD\uFFFD\u006E\u004E\u0027\uFFFD\uFFFD\u0006\uFFFD\uFFFD\uFFFD\uFFFD\u0000\u0021\u0029\u007A\u0076\u005C\uFFFD\u0000\uFFFD\u006C\u0078\u0046\uFFFD\u0064\uFFFD\uFFFD\uFFFD\uFFFD\u0042\u007E\u006F\uFFFD\u0021\u0003\u0027\u0075\u001B\u006B\u0036\u0001\uFFFD\uFFFD\uFFFD\u000D\uFFFD\u0003\u0049\u0035\u007F\uFFFD\uFFFD\uFFFD\uFFFD\u0062\uFFFD\u007D\uFFFD\u0018\u0040\uFFFD\u006F\uFFFD\uFFFD\u002A\uFFFD\uFFFD\u000A\uFFFD\uFFFD\uFFFD\u0013\u0004\u003B\uFFFD\u0010'
+  )
+  t.end()
+})
+
+test('utf8 replacement chars for anything in the surrogate pair range', function (t) {
+  t.equal(
+    new B([ 0xED, 0x9F, 0xBF ]).toString(),
+    '\uD7FF'
+  )
+  t.equal(
+    new B([ 0xED, 0xA0, 0x80 ]).toString(),
+    '\uFFFD\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xED, 0xBE, 0x8B ]).toString(),
+    '\uFFFD\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xED, 0xBF, 0xBF ]).toString(),
+    '\uFFFD\uFFFD\uFFFD'
+  )
+  t.equal(
+    new B([ 0xEE, 0x80, 0x80 ]).toString(),
+    '\uE000'
+  )
+  t.end()
+})