A reversed-phase high performance liquid chromatographic (HPLC) procedure for the analyses of 3,4,4'-trichlorocarbanilide (TCC) and its free and/or conjugated metabolic products in plasma/serum in described. A rapid, effective clean-up procedure, prior to chromatographic evaluation, involves a single-step combined protein removal and THF extraction. Detection of the TCC moiety after HPLC separation is by UV absorption at 265 nm; quantitation by peak height measurement. A detection limit of 10 ppb of TCC and/or metabolities has been demonstrated for this method. Verification of this method was by radiotracer counting of the appropriate HPLC peaks from plasma of animals adminstered 14C-TCC/TCC. The utility of this method was demonstrated in both animal pharmacological and toxicological studies and in human bathing studies.