Twelve male medical and graduate students received dextroamphetamine sulfate in doses of 0, 5, 10, and 15 mg/70 kg body weight. The study was conducted in a double-blind manner, and treatments were assigned according to randomized, complete block design. The drug was given orally and subjects were instructed not to eat 3 1/2 h prior to administration. After administration, total urine output was collected for 12 h; no attempt was made to control urinary pH to more realistically approach the general clinical usage of amphetamines. The urine was pooled into two 6-h segments and analyzed for amphetamine concentration. Subjective impressions of the treatments were also evaluated by means of the Cornell Medical Index Questionnaire. Results showed that approximately 30% of the total dose was excreted unchanged within 12 h after administration. The amount excreted agreed very closely with the doses given and paralleled the scores for subjective impressions by the subjects. None of the subjects felt that their driving would be impaired for any of the doses administered. This study indicates that under ordinary conditions (in which pH is not artificially controlled), therapeutic doses of dextroamphetamine can be detected in urine for up to 12 h after oral administration.