OBJECTIVE: The timing and clinical correlates of symptom change following antipsychotic treatment were examined in first-episode and chronic schizophrenia. METHOD: The subjects were 36 first-episode schizophrenic patients who had received minimal or no neuroleptics and 34 patients with chronic illness whose neuroleptics had been withdrawn. They were followed for 2 years and assessed with the Scale for the Assessment of Positive Symptoms and the Scale for the Assessment of Negative Symptoms. Treatment decisions during follow-up were made clinically by the treating physicians. RESULTS: At 6-month follow-up, both the neuroleptic-naive and previously treated patients showed significant improvement in positive symptoms (52% and 44% reductions from baseline, respectively). The previously treated but not the neuroleptic-naive patients also showed a significant reduction in negative symptoms (19% from baseline). A longer duration of illness before baseline assessment and inconsistent treatment during follow-up were independently associated with poorer treatment outcome in terms of positive symptoms in both groups. There were no significant changes on the outcome measures in either group after the 6-month follow-up. CONCLUSIONS: The results suggest that maximum symptomatic improvement occurs within the first 6 months of treatment and that disease progression may blunt treatment efficacy in both first-episode and chronic schizophrenia.Abstract Teaser