Plasma diazepam levels were estimated by gas-liquid chromatography following a single 10 mg dose administered to a health adult female population by the oral and intramuscular routes. The highest levels were achieved following oral administration, reaching a peak at 60 minutes, although injection into the thigh resulted in a more rapid rise initially. Injection into this site produced higher levels than when the buttock was used. Injection by nurses into the latter site produced particularly low plasma levels over the 90-minute period of study. The plasma levels found at 90 minutes following the oral and thigh routes were found to be closely correlated with the weight of the patient.