We determined the prevalence of adverse drug events (ADEs) in a general teaching hospital in Rabat, Morocco. We performed a 5-day cross-sectional study of hospital departments recruiting inpatients and outpatients. Among the 1390 patients surveyed, 59 (4.2%) experienced at least 1 ADE and for 20 patients (1.4%) the ADE was responsible for hospitalization or prolongation of hospitalization. The ADE was classified as serious in 28 patients. Of the total of 76 ADEs, 10 (13.2%) were categorized as preventable; 6 of these occurred during the treatment monitoring phase. Patients who experienced an ADE were more likely to be women, to be younger (< 30 years) and to be hospitalized in medical departments.