The excretion patterns, tissue levels, and ionexchange chromatography of the urinary metabolites of Mobam have been determined in rats. Rats (two groups, 14 per group) were dosed with Mobam-14C (ring-labeled) at 2.0 and 13.0 mg. per kg. of body weight. After 24 hours, 87% (2.0 mg. per kg.) and 76% (13.0 mg. per kg.) of the 14C dose were excreted as water-soluble compounds in the urine. Carcasses of rats from both groups sacrificed at 3 days contained less than 1.0% of the radioactive dose. Tissue residues were fairly evenly distributed, decreasing in the 13.0 mg. per kg. group from an average of 0.5 p.p.m. (wet tissue) after 2 days to 0.2 p.p.m. after 8 days. Anion exchange chromatography on AE cellulose separated the radioactivity in the urine into four fractions. Two metabolites in the urine, 4-benzothienyl sulfate and 4-benzothienyl glucuronide, accounted for 83 and 87% of the excreted 14C from rats dosed at 2.0 and 13.0 mg. per kg., respectively. These metabolites were isolated and purified by liquid ion-exchange chromatography, paper chromatography, gel filtration, and gas-liquid chromatography. © 1969, American Chemical Society. All rights reserved.