This study in Saudi Arabia explored the determinants of physicians’ prescribing behaviour in primary care in Riyadh city. A self-administered questionnaire designed to explore factors influencing prescribing (sociodemographic factors; practice setting; continuing education; access to educational materials; pharmaceutical company representatives; and patient factors) was completed by 87 PHC physicians. A factor analysis of 56 variables extracted 7 factors that explained 46% of the variance. Of these, 4 components positively related to perceived good prescribing behaviour could be summarized as clinical experience of physicians; use of educational materials for continuous updating of medical knowledge; enhanced levels of continuing medical education and willingness to involve patients in decision-making; and working as a team using pharmacists for consultation and emphasizing the role of medical education. The other 3 factors derived from the analysis were less easy to interpret and may have been statistical anomalies (or measurement errors).