Following administration of [14C]-labeled 9-aminoacridine ([14C]9AA) hydrochloride either orally or intravenously to rats, the excretion of radioactivity was similar, with 20-26% of the dose appearing in the urine and 57-68% in the feces. The pattern of tissue distribution was also similar for the two routes. This information suggests that absorption of the oral doses was extensive and that, for both routes of administration, biliary excretion accounted for most of the radioactivity in the feces. Biliary excretion of radioactivity derived from [14C]9AA was confirmed in an experiment involving rats with inserted biliary cannulas. For these rats, 49.5% of the dose administered appeared in the bile in 4 h. The major urinary and biliary metabolite of [14C]9AA of rats was identified as an O-beta-glucuronide of hydroxylated 9AA. Absorption of 9AA through the skin could not be conclusively demonstrated. For monkeys dosed topically with [14C]9AA, only small amounts of radioactivity (a total of less than 0.8% of the dose) appeared in the urine and various tissues in 24 h.