A new psychotropic drug (P-4657B, Thiothixene) was tried in 14 patients with chronic syndromes (12 schizophrenics, one oligophrenic with psychotic reaction and one with involutional depression). The dosis varied between a minimal of 20 mg to a maximal of 75 mg per dien, per os, for 22 to 130 days. The results were as follows: very good improvement in two cases; three cases with good results; 8 cases remained unchanged and one case impaired. The best results, on account of the symptoms, were observed on the interpersonal communication and on pragmatism. Severe side effects were not present. Neurodisleptic manifestations, in mild degree, were observed only in three cases. The authors concluded that the Thiothixene is a useful neuroleptic in the treatment of chronic mental syndroms, specially in schizophrenics with bad personal communication and apragmatism. They also suggest the trial in acute psychosis.