Intravenous injections of gammahydroxybutyric acid (GHBA) (150-200 mg/kg) induce desynchronized sleep (DS) in the cat. This was shown by recording the EEG, eye-movements, the neck EMG, heart-rate and arterial pressure. The decreases in arterial pressure were not different from those recorded during naturally occurring DS. GHBA, given at doses above 200 mg/kg induced anaesthesia, during which arterial pressure was elevated. At the end of GHBA-induced sleep or anaesthesia there was a stage during which the animals were ataxic. The EEG showed a hypersynchronous spike pattern and arterial pressure was markedly elevated.