Methaqualone injected i.v. has been reported to be a safe short-acting anaesthetic agent and a muscle relaxant in man. It has been employed in a variety of operative procedures and to modify convulsions in the management of tetanus and in electroconvulsive therapy. Safety, usefulness and the marked central effects of the drug led us to study its central effects by EEG in man. Discrepancies between clinical and EEG signs were thus seen. EEG patterns resembled those after barbiturates and the effect was dose dependent. Differences between methaqualone and barbiturates are discussed. The EEG patterns were potentiated by thioridazine and antagonised by imipramine.