Physicians’ prescribing behaviour is closely linked with patient safety and this area is poorly researched in Saudi Arabia. The objective of this study was to analyse physicians’ prescribing patterns and the adequacy of noted information in the primary health care sector in Riyadh city. All medication prescriptions from 5 public (n = 1182) and 5 private (n = 1200) health centres were collected by simple random sampling during 1 working day. Antibiotics were the most commonly prescribed drugs in both sectors. The mean number of drugs per prescription was 2.08 and 2.36 in the public and private sectors respectively. Information and instructions noted on prescriptions varied considerably between private and public health centres. Similarly the medication prescribing pattern differed across the 2 health settings. Primary care physicians in Saudi Arabia need continuing training to improve their prescribing practices.