Maximal urinary excretion of unchanged cocaine occurred within 2 h of the intranasal absorption of 1.5 mg/kg body weight of cocaine hydrochloride, and diminished rapidly thereafter. Excretion of benzoylecgonine was maximal 4 to 8 h following administration of the drug and diminished slowly over an interval of several days. Peak cocaine and benzoylecgonine concentrations observed were 24 and 75 microgram/ml, respectively. Benzoylecgonine/cocaine ratios were too varied to allow estimation of cocaine concentrations from benzoylecgonine concentration data or vice versa. Benzoylecgonine concentrations generally exceeded the corresponding cocaine values by a wide margin, but excretion of free cocaine in the absence of benzoylecgonine was observed in one subject. Cocaine was generally detected for only approximately 8 h, and for a maximum of 12 h, whereas benzoylecgonine was generally detected by chromatographic or enzyme immunologic assays for 48 to 72 h. Benzoylecgonine was positively identified in urine by raidoimmunoassay for 96 to 144 h after dosing.