A dominant lethal mutagenicity study was performed in rats with the following chemicals that may be used to dye hair: 2-nitro-p-phenylenediamine, 4-nitro-o-phenylenediamine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, p-toluenediamine, 2,4-diaminoanisole, 2,5-diaminoanisole, 2-amino-4-nitrophenol, 2-amino-5-nitrophenol, and 4-amino-2-nitrophenol. The compounds were administered intraperitoneally three times weekly for 8 weeks to groups of 20 sexually mature Charles River CD male rats at a dose of 20 mg/kg. This amount of dye is an enormous exaggeration of the human exposure from brief montly topical application of a hair color product containing 2 g (40 mg/kg) or less total dye. There was no evidence of an increase in postimplantation fetal loss which could indicate a dominant lethal effect. Included are data on the acute toxicity of the dyes by various routes of administration in different vehicles.