Four polar metabolites were isolated from the urine of human subjects orally treated with tripelennamine, and their structures elucidated by various chemical and physical methods. One of the metabolites, which is a minor one, was identified as an N-oxide of tripelennamine, and the other three as glucuronide conjugates. One of the conjugates, which is a major metabolite, has been assigned a unique quaternary ammonium N-glucuronide structure, since it gave tripelennamine and D-glucuronic acid on incubation with beta-glucuronidase. The N-oxide, which has also been prepared synthetically, remained unchanged on similar treatment. The other two conjugates were O-glucuronides of hydroxylated derivatives, the glucuronide of hydroxytripelennamine being the principal metabolite. No desmethyltripelennamine was found in the urine, however. Hydroxylation in both cases had occurred in the pyridine ring.