The triazolobenzodiazepine estazolam can be quantitated by gas chromatography with electron-capture detection. After addition of a suitable internal standard, plasma samples are extracted into toluene-isoamyl alcohol or benzene-isoamyl alcohol. The organic extract is separated, evaporated to dryness, reconstituted, and chromatographed using a 50:50 methyl-phenyl column (SP-2250). The sensitivity limit is approximately 1 ng of estazolam in a 1-ml sample. The method is suitable for clinical or experimental pharmacokinetic studies.