The effects of BAS, the benzyl analog of serotonin, were studied on 24 chronic, moderately disturbed female psychotic patients. The most prominent beneficial action, that of tranquilization, was noted in 22 of these patients. Tranquilization was attained at dosage levels varying between 50 to 200 nag/day. The maximum tolerated dose was 300 mg/day. Among the paranoid patients who improved, the delusions became less important The intensity and frequency of the hallucinatory experiences diminished. In hebephrenic patients, speech became less dissociated. These salutary psychiatric effects, however, were marred by untoward reactions involving the general health of some patients who lost weight chiefly because of a profound feeling of weakness and fatigue. Another disturbing side reaction deserving comment is ataxia which was extensive in some patients. The effects of BAS are compared with those of reserpine which they resemble in many ways, but are not seen to the same extent with both drugs. The clinical similarities of BAS and reserpine are ascribed to the indole group, which their chemical structures have in common. Their different nonindolic moieties are regarded as being the causes for the clinical dissimilarities exhibited by these two drugs.