Acute agranulocytosis is a rare, potentially life-threatening condition, which is attributable to drugs in > 70% of cases. Agranulocytosis is characterised by a peripheral neutrophil count < 0.5 x 10(9)/l. It often manifests with a severe sore throat, but isolated fever, pneumonia or septicaemia are not uncommon. Agranulocytosis may be caused by many drugs. High-risk drugs include antithyroid drugs, clozapine, ticlopidine, sulfasalazine, dipyrone, trimethoprim/sulfamethoxazole, carbamazepine and probably rituximab. Suspect drugs should be stopped immediately. In febrile patients, blood cultures and, where indicated, site-specific cultures should be obtained and treatment with empirical broad spectrum antibiotics started. Haematopoietic growth factors should be considered in patients with poor prognostic factors (e.g., a neutrophil count < 0.1 x 10(9)/l), severe clinical infection or severe underlying disease or comorbidity. Case fatality has decreased to ~ 5% in recent years, probably owing to improved intensive care treatment and increased alertness of physicians to this severe adverse reaction.