Cocaine was given by intravenous administration to human subjects and the concentrations in plasma were measured by gas chromatography--mass spectrometry. Many pharmacokinetic parameters were found to have a strong dose dependence over the range 1 - 3 mg/kg. The terminal plasma half-life in minutes is given by the equation t1/2(beta) = 13.5 + 24.5 dose (r = 0.946). The total plasma clearance in liters/kg per h is 2.51--0.67 dose (r = -0.973). From analysis of previously published data the absorption half-life t1/2(ab) is approximately 8 min for gastrointestinal and for nasal inhalation absorption. The bioavailability for nasal inhalation is approximately 60%. While routes of administration for modern recreational use could lead to unexpected drug accumulation in the blood it is not likely to occur from chewing coca leaves.