Chlorpromazine has now been used in the treatment of schizophrenia for 11 years. At least ten other phenothiazines have been developed and are in medical use in the treatment of schizophrenia. There are still important questions concerning the extent of the clinical effects of chlorpromazine; moreover, there are a much larger number of questions concerning the real clinical differences between chlorpromazine and the newer phenothiazines. The nine-hospital collaborative study of phenothiazine drugs in acute schizophrenic reactions reported here was designed principally to answer these questions in as thorough a manner as current scientific methodology would permit. The present report will present detailed findings relevant to the following clinical questions: 1. What proportion of acute schizophrenic patients showclinicallysignificant improvement on phenothiazine treatment? Even after improvement, to what extent are patients still mentally ill? 2. Do the active drugs differ in their effects on specific schizophrenic symptoms? For example, is