Main objective—To quantify prescribing patterns of physicians during their year of social work in health centers of Bogotá, Colombia, for three tracer conditions: acute respiratory infection (ARI), systemic hypertension (SH) and acute diarrhea (AD). Design—Cross‐sectional survey. Setting—Primary Care Health Centers in the city of Bogotá. Strategy—The Health District Department of Bogotá (Secretaria Distrital de Salud) provided the sampling frame of SILOS (Local Health System) and UPAS (primary health service units) with a physician in the social work year. Samples of patient–physician encounters for the three tracer conditions within UPAS were examined, and detailed information collected on prescription indicators. Results—Information was collected on a total of 1099 patient–physician encounters. Results show that 61% (95% CI: 58.6–63.1) of prescriptions in these settings are non‐generic, and only 62% (95% CI: 59.5–64.0) are from the Colombian essential drug list. Number of medications prescribed per encounter were higher with ARI, as well as prescriptions for non‐generic forms, antibiotics, and medications outside of the Colombian essential drug list. Inappropriate prescriptions were seen in 31% (95% CI: 28.1–33.7) of all encounters. Discussion—Inadequacy of prescriptions (based on diagnosis) suggest that the teaching of rational prescribing patterns should be targeted with much more emphasis in schools of medicine. Interventions focused on the outstanding deficiencies should be designed and properly evaluated. © 1998 John Wiley & Sons, Ltd.