Five years after its introduction at a state mental hospital, an automated drug exception review system continues to show a long-term impact on the prescribing practices of hospital physicians. Although the overall rate of exceptions has remained low, approximately 25% of all new exceptions pointed out by the computer result in a change in the order by the physician. The fact that 60% of new exceptions are justified suggests that some forms of polypharmacy may be appropriate. The integration of the exception-reporting system into the clinical review process has avoided the danger of the computer's being seen as an adversary to the clinician or as exerting undue control over psychopharmacologic prescription practices.