Studies have shown that schizophrenics respond to the reinstatement of neuroleptics in a characteristic pattern, but there is disagreement about the mechanism underlying symptom change. To clarify this issue, double- blind, serial measurements of the behavior and symptom change of schizophrenic subjects who resumed neuroleptic medication after a drug- free period were analyzed. Fifty percent of the response occurred by the seventh day of post-drug reinstatement, including a significant improvement in symptom/behavior inventory subscales measuring delusions, hallucinations, and other positive symptoms associated with psychosis.