Index: src/OFMutableString.h
==================================================================
--- src/OFMutableString.h
+++ src/OFMutableString.h
@@ -120,10 +120,31 @@
  *
  * \param range The range of the characters which should be removed
  */
 - (void)removeCharactersInRange: (of_range_t)range;
 
+/**
+ * Removes the characters at the specified range.
+ *
+ * \param start The index where the replacement should be started
+ * \param end The index until which the characters should be replaced.
+ *	      This points BEHIND the last character!
+ * \param repl The string to the replace the characters with
+ */
+- (void)replaceCharactersFromIndex: (size_t)start
+			   toIndex: (size_t)end
+			withString: (OFString*)repl;
+
+/**
+ * Removes the characters at the specified range.
+ *
+ * \param range The range of the characters which should be replaced
+ * \param repl The string to the replace the characters with
+ */
+- (void)replaceCharactersInRange: (of_range_t)range
+		      withString: (OFString*)repl;
+
 /**
  * Replaces all occurrences of a string with another string.
  *
  * \param str The string to replace
  * \param repl The string with which it should be replaced

Index: src/OFMutableString.m
==================================================================
--- src/OFMutableString.m
+++ src/OFMutableString.m
@@ -385,10 +385,48 @@
 - (void)removeCharactersInRange: (of_range_t)range
 {
 	[self removeCharactersFromIndex: range.start
 				toIndex: range.start + range.length];
 }
+
+- (void)replaceCharactersFromIndex: (size_t)start
+			   toIndex: (size_t)end
+			withString: (OFString*)repl
+{
+	size_t nlen;
+
+	if (isUTF8) {
+		start = of_string_index_to_position(string, start, length);
+		end = of_string_index_to_position(string, end, length);
+	}
+
+	if (start > end)
+		@throw [OFInvalidArgumentException newWithClass: isa
+						       selector: _cmd];
+
+	if (end > length)
+		@throw [OFOutOfRangeException newWithClass: isa];
+
+	nlen = length - (end - start) + [repl cStringLength];
+	string = [self resizeMemory: string
+			     toSize: nlen + 1];
+
+	memmove(string + end, string + start + [repl cStringLength],
+	    length - end);
+	memcpy(string + start, [repl cString], [repl cStringLength]);
+	string[nlen] = '\0';
+
+	length = nlen;
+}
+
+- (void)replaceCharactersInRange: (of_range_t)range
+		      withString: (OFString*)repl
+{
+	[self replaceCharactersFromIndex: range.start
+				 toIndex: range.start + range.length
+			      withString: repl];
+}
 
 - (void)replaceOccurrencesOfString: (OFString*)str
 			withString: (OFString*)repl
 {
 	const char *str_c = [str cString];

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -287,10 +287,21 @@
 				      toIndex: 4]) &&
 	    [s[0] isEqual: @"𝄞bä€"] &&
 	    R([s[0] removeCharactersFromIndex: 0
 				      toIndex: 4]) &&
 	    [s[0] isEqual: @""])
+
+	TEST(@"-[replaceCharactersFromIndex:toIndex:withString:]",
+	    (s[0] = [OFMutableString stringWithString: @"𝄞öööbä€"]) &&
+		   R([s[0] replaceCharactersFromIndex: 1
+					      toIndex: 4
+					   withString: @"äöü"]) &&
+	    [s[0] isEqual: @"𝄞äöübä€"] &&
+	    R([s[0] replaceCharactersFromIndex: 0
+				       toIndex: 7
+				    withString: @""]) &&
+	    [s[0] isEqual: @""])
 
 	EXPECT_EXCEPTION(@"Detect OoR in "
 	    @"-[removeCharactersFromIndex:toIndex:] #1", OFOutOfRangeException,
 	    {
 		s[0] = [OFMutableString stringWithString: @"𝄞öö"];