A rapid and sensitive method is described for the determination of CGS-8216 (a pyrazoloquinoline that displaces benzodiazepines from their binding sites in the brain but which reverses some of the behavioural actions of the benzodiazepines) in plasma using high-performance liquid chromatography with ultraviolet detection. CGS-9896 serves as the internal standard. The method is applied to a pharmacokinetic study of CGS-8216 in the rat. CGS-8216 was not detectable in plasma 24 h after a single IP administration of a 10 mg/kg dose. Animals treated with five once-daily injections of CGS-8216 had plasma concentrations 30 min after the final injection that were approximately four-times those observed 30 min after a single treatment. This suggests that caution must be used in the interpretation of results from experiments using multiple administrations of CGS-8216. The compound could not be detected in brain tissue at any of the time points studied.