The application of reversed-phase high-performance liquid chromatography to the measurement of benzoylecgonine and cocaine in urine is described. Following a simple extraction and clean-up procedure, chromatography is performed using a column containing an octadecylsilica coated packing, elution with 17% acetonitrile in pH 2.7 phosphate buffer and ultraviolet detection at 200 or 235 nm. The detection limit is ca.0.1 microgram of drug per ml urine, and using the ethyl ester of benzoylecgonine as an internal standard, benzoylecgonine and cocaine are quantified with coefficients of variation of 7.0 and 2.8%, respectively. The procedure has been applied to urines from subjects receiving intranasal cocaine, and compared to the enzyme multiplied immunoassay technique. The chromatography procedure also permits the separation of norcocaine and benzoylnorecgonine.