MutantMaker helps researchers performing site directed mutagenesis screen their potential mutants with restriction enzyme digests rather than costly sequencing. The oligonucleotide sequences suggested by MutantMaker will create or destroy restriction sites while both creating the desired mutant and retaining flanking amino acids. Using a simple and elegant user interface, researchers enter their original DNA sequence into a text field, drag a codon selector over the codon to mutate, and choose how to mutate their selected amino acid. MutantMaker has 492 unique restriction enzymes built right in, not including isoschizomers! Users can select any set of enzymes based on commercial availability or size. MutantMaker results are even multi-colored showing exactly which nucleotides were mutated. In typical fashion, results can be saved and reloaded for later use. And for reliability, data files are human-readable XML.