Findings in this study support earlier investigations in attesting to the antipsychotic efficacy and relatively low toxicity of pipotiazine palmitate. Results with all efficacy measures utilized were consistent in indicating a high level of efficacy for this investigational compound. Pipotiazine palmitate apparently has an average duration of action that extends beyond 4 weeks in severely ill schizophrenic patients. This particular long acting IM antipsychotic preparation appears to have an even longer duration of activity than some of the other available standard long acting agents. The optimal dosage range for severely ill schizophrenic patients appears to be between 100 and 600 mg once monthly. While this type of drug (as is the case with many antipsychotic drugs) does reduce the psychotic symptomatology and improves the thought associations sufficient to enable the patient to leave the hospital, it should be re-emphasized that socioeconomic and guidance counseling services are necessary to maintain the patient in the community. The availability of this type of long acting preparation is not only economical in terms of nursing care and hospital cost but it should also increase the efficacy of psychopharmacologic treatment of schizophrenics by reducing both patient errors and staff errors in administration of medication. In addition, this IM preparation should prove to be of invaluable help in maintaining the schizophrenic patient in his community by reducing the relapse and the rehospitalization rates. It should be noted that there are schizophrenic patients who either absorb compounds from the gastrointestinal tract in a very poor manner or too rapidly metabolize the antipsychotic agents with resultant suboptimal blood levels and these subjects may be called "drug refractory." This type of long acting medication is an ideal preparation for the schizophrenic patient who has these types of absorption or metabolic problems since the "circulatory pass" through the liver is minimal after IM medication as compared to that encountered by an orally administered agent. The clinical disadvantage of pipotiazine palmitate is the delay in onset of therapeutic activity after injection. Significant improvement is first noted after 3 to 4 days after the highest IM dosage administration. Therefore, it may be necessary to use an oral or IM preparation of a neuroleptic with a more rapid onset of activity or utilize an oral dosage of the pipotiazine salt during the first week following IM administration of pipotiazine palmitate.