Between January 1974 and June 1975 52 in-patients with mania were treated with Clozapine. In one half of the patients this was the only drug throughout. It was so far thought to be indicated mainly for schizophrenics. Its main action mostly was immediate (partly on the first or second day) and was characterised by initial sedation and subsequent improvement of increased motivation and flight of ideas. On the basis of our present experience Clozapine appears to be superior in the treatment of mania in its main and side effects. Patients prefer it often because of the absence of extrapyramidal side-effects. The in-patient treatment was on average much shorter with Clozapine than with other drugs. These first observations demand further tests for this specific indication.