Divalproex sodium has been approved for use in treating bipolar disorder. Its usefulness in schizophrenia has yet to be adequately assessed. Three days after initiating haloperidol treatment, patients who were hospitalized for an acute exacerbation of schizophrenia received either valproate augmentation (early-augmentation group) or continued to receive haloperidol alone (no-augmentation group). Patients in the no-augmentation group who failed to respond 14 days after the dose of haloperidol reached 20 mg/day received valproate augmentation (delayed-augmentation group). By day 14, the early-augmentation group improved 32.4% more than the no-augmentation group. Fifty percent of the patients in the no-augmentation group failed to respond to haloperidol alone for 2 weeks. They improved by 29% upon the addition of valproate. Compared with those who received no or delayed augmentation, the early-augmentation group required 44.8% fewer inpatient days from the initiation of haloperidol treatment. Patient response to treatment was particularly noted in suspiciousness, hallucinations, unusual thought content, and emotional withdrawal. Early augmentation with valproate may reduce the length of inpatient stays and provide substantially better therapeutic outcomes. It is, however, premature to recommend changes in the standard clinical management of schizophrenia on the basis of the data provided herein, in view of the small sample and open-label nature of the report.