In a retrospective study, 19 cases classified as idiosyncratic drug-induced agranulocytosis were found among 162 files of patients hospitalized in internal medicine clinics of the university hospital where this diagnosis had been coded. This would give an estimated incidence of 2.6 cases per million inhabitants per year for the Geneva area. In most cases several drugs were implicated in causation of the episodes. Suspected drugs were those commonly reported in the literature, but also some drugs which might already have been taken to treat infectious complications of agranulocytosis. A comparison of the Geneva cases with those notified to the Swiss Intercantonal Office for the Control of Medicines reveals a similar profile of involved drugs.