The clearance profile and tissue distribution of 2 occupational toxicants, 3,3',4,4'-tetrachloroazobenzene (TCAB) and 3,3',4,4'-tetrachloroazoxybenzene (TCAOB), were examined in male Sprague-Dawley rats. TCAB was found to be cleared from the body more rapidly than TCAOB when a single dose of 14C-labeled TCAB or TCAOB was administered orally. While 66% of the administered TCAB dose was excreted via the urine and feces within the first 24 h, TCAOB-treated animals were only able to clear 37% of the administered dose by the same elimination route. The half-lives for elimination of TCAB and TCAOB were estimated to be 18 h and 34 h, respectively. Examination of the tissue distribution of the remaining radioactivity indicated that, for both compounds, the adipose tissue contained the highest level of radioactivity. The rapid elimination of TCAB and TCAOB by rats may explain in part the reduced toxicity of these 2 compounds to whole animals in comparison to the isosteric 2,3,7,8-tetrachlorodibenzo-p-dioxin.