This study sought to assess the common practice of combination tranquilizer therapy in chronic psychotics. Conducted under double-blind conditions, it compared the efficacy and side effects from 3 regimens over a course of 8 months: 1. Chlorpromazine plus trifluoperazine; 2 Chlorpromazine plus trifluoperazine placebo; and 3. Trifluoperazine plus chlorpromazine placebo. It showed that with the two drugs combined efficacy was greater than with these drugs used individually. It showed, too, that with the drugs in combination side effects were about half what they were with trifluoperazine and not much more than they were with chlorpromazine (18% and 12% respectively). Therefore, from this study, it appears that the combination of chlorpromazine and trifluoperazine offers advantages in patients who do not respond to treatment with a single tranquilizer or who develop limiting side effects on high doses of a single tranquilizer.Abstract Teaser