4-Chloro-o-phenylenediamine is a chlorinated aromatic amine that exists as a brown crystalline solid or powder at room temperature. 4-Chloro-o-phenylenediamine can be used as an oxidation base for dye preparation, as a chemical intermediate to produce 5-chlorobenzotriazole, as a curing agent for epoxy resins, as a reagent in gas chromatography, and to synthesize experimental pharmaceuticals. It has been used as a chemical intermediate in dye production and was patented as a hair-dye component. Oral exposure to 4-chloro-o-phenylenediamine caused tumors in two rodent species and at several different tissue sites. Dietary administration of technical-grade 4-chloro-o-phenylenediamine caused benign or malignant liver tumors (hepatocellular adenoma or carcinoma) in mice of both sexes and benign or malignant tumors of the urinary bladder and forestomach (papilloma or carcinoma) in rats of both sexes (NCI 1978).