Forensic chemists are expected by U.S. courts to identify with great accuracy the drug of abuse found in evidence. When identifying cocaine, the forensic chemist must be aware of the chemical taxonomy of the coca plant, for impurities can arise from the constituents of the plants as well as from the manufacturing process or from adulteration. The article reports on advances in presumptive testing and in chromatographic methods that have made it possible to screen samples rapidly. Forensic laboratories now make routine use of such methods as gas-liquid chromatography, electron impact mass spectrometry, and proton magnetic resonance spectrometry to improve the detection and identification of cocaine in illicit drug samples. 81 references. (Author abstract modified)