Objectives: To identify and quantify deficiencies in the prescribing/ordering of inpatient and discharge medications and determine strategies to address them. Design and setting: A descriptive study in medical and surgical wards at a tertiary referral teaching hospital. Patients: All available inpatients in 12 medical and 2 surgical wards on two consecutive days and all discharges on a single day. Results: Medication orders for 230 inpatients and 68 discharge patients were audited. A total of 2978 inpatient orders were reviewed including 634 'once only' doses, 1840 regular and 504 'as required' medications. Errors in physician prescribing occurred at a frequency of 25/1000 prescriptions and included 48 ( 1.6%) incorrect, ambiguous or unspecified doses and four prescriptions where the specific oral form was not stated. In 14 (0.5%) cases, the dosing frequency specified was wrong, unclear or absent and there were three cases of duplication. Two patients were prescribed drugs to which they had a documented allergy. Details of previous adverse drug reactions were complete in only 14 of 62 (23%) patients. Of the 68 discharge prescriptions audited, orders for 49 of 329 regular medications (15%) had been unintentionally omitted (range 1-8 medications per patient). Conclusions: The audit identified limitations in the quality of prescribing/ordering which were in part due to deficiencies in the current medication chart and discharge summary. To address these limitations, the medication ordering system has been revised and a multidisciplinary educational program implemented to promote safe and explicit prescribing.Aust J Hosp Pharm 2001; 31: 102-6.