Rational prescribing is associated with improved safety in drug use, better quality of life for patients and cost-effective care. Medication prescribing is a relatively unexplored area of research in Saudi Arabia and until now most studies have been in the secondary and tertiary health care system. This paper is the first of 3 review articles that form the background for a series of 5 interconnected studies of prescribing patterns and medication errors in the public and private primary health care sectors of Saudi Arabia. A MEDLINE search was conducted to identify papers published in peer-reviewed journals over the previous 3 decades. The paper reviews variations in prescribing patterns and influences on physicians’ prescribing behaviour worldwide and in Saudi Arabia.