The drug prescribing pattems of ambulatory care physicians in the Ministry of Health (MOH) hospitals were studied by examining 10,291 systematically sampled prescriptions obtained from 22 general hospitals covering the various health regions within Saudi Arabia. An audit of prescription information revealed that documentation was not generally complete. Information relating to patient age and diagnosis was missing in 18.6% and 9.8% of the prescriptions, respectively. The average number of drugs per prescription was 2.1 +/- 0.95. The most frequently prescribed drug categories were systemic anti-infectives, analgesics/antipyretics, and vitamin preparations, respectively. Paracetamol, ampicillin, antacid preparations, and vitamin B complex were the specific drugs that ranked high in the frequency of prescription. The pattems of drug use observed in this study indicate a trend for the overprescribing of certain categories of drugs. The need to improve current drug policy and drug prescribing is discussed with a recommendation for the establishment of a Pharmacoepidemiology Unit to monitor drug use in Saudi Arabia.