Cerebral blood flow (CBF) was measured with the 133Xenon inhalation technique and forehead skin flow with laser Doppler, before and twice after 0.3 milligram/kilogram of cocaine hydrochloride and a placebo given intravenously to six cocaine abusers, during two visits, separated by a minimum of one week. After cocaine, subjects showed significant increases in intoxication and tension. Systolic blood pressure and pulse rate also increased significantly after the drug but not after the placebo. CBF, with and without correction for end-tidal CO2, showed increases in left and right hemisphere after cocaine. The CBF increase was maximal in frontal, central and parietal regions. CBF changes correlated only with changes in a rated level of intoxication. Forehead skin flow did not change after cocaine or placebo. In habitual cocaine abusers, 0.3 mg/kg of cocaine, given intravenously produced increased CBF and no changes in forehead skin flow.