The disposition and metabolism of 14C-labeled 4-chloro-2-nitroaniline (CNA) was studied in male F344 rats following oral or intravenous (iv) administration. The gastrointestinal absorption of CNA was found to be near complete and was not affected by the dose in the range studied (0.788-78.8 mumol/kg). Following either oral or iv administration, CNA was rapidly distributed throughout the tissues and showed no marked affinity for any particular tissue. [14C]CNA was rapidly cleared by metabolism and excretion in urine and to a lesser extent in feces. The whole-body half-life of CNA in the rat was approximately 1 h, and clearance of radioactivity from the body was near complete in 3 d. The known carcinogen and potential metabolite of CNA, 4-chloro-o-phenylenediamine, was not detected in rat tissues or excretia following administration of CNA. Approximately 70% of the dose was detected in urine as a sulfate conjugate of a single metabolite of CNA. The remainder of the dose was excreted in the form of seven additional metabolites and a trace of the parent compound. CNA-derived radioactivity had little potential for bioaccumulation, and there was no evidence for saturation of any mechanism involved in the absorption, distribution, metabolism, or excretion of CNA in the dose range studied.