A method for the analysis of ketamine and of its metabolites is described using gas-liquid chromatography for separation and flame ionization detection. The lower limit of detection for ketamine in serum was 0.025 mug/ml. The pharmacokinetic behaviour of ketamine after intravenous injection may be described in terms of an open two-compartment model. The serum half-life of ketamine was in alpha-phase about 11 min, the predominant half-life for the beta-phase 2.5 h. The half-life of ketamine and its metabolities in urine was comparable to that in serum. It could be shown that the duration of anaesthesia is not only correlated ti ist rapid metabolic breakdown and elimination, but also to the distribution of the drug peripheral tissue.