Fifty-seven newly admitted schizophrenic men were treated with a butyrophenone derivative, triperidol, for 6 weeks. Daily doses, following a brief period of initial build-up, ranged between 1.5 and 12 mg. Treatment was evaluated by 2 rating scales, the BPRS and the IMPS. Significant improvement was noted in 13 of the 16 symptoms scored on the BPRS, on all 10 factors of the IMPS, and on each of 4 syndrome factors derived from the BPRS. The BPRS total pathology change score of 28.0 was comparable to change scores obtained in previous studies of potent phenothiazine antipsychotics in similar patients.Classification of these patients into 3 types, "paranoid," "schizophrenic" and "depressed" on the basis of computer analysis of pre-treatment rating profiles showed that triperidol had a specifically beneficial effect in the former group. Not only does this finding further substantiate the idea that antipsychotic drugs have differing effects on various schizophrenic sub-types, but suggests that in triperidol, we have the most effective drug available for this particular group.Side effects from triperidol were largely due to extrapyramidal syndromes, sedation, paradoxical excitement and anticholinergic effects. The neurological side effects appeared to be qualitatively similar to those from phenothiazines, but perhaps more frequent at the doses of drug used.