Drug-induced agranulocytosis may be type I (involving the drug, antibodies and neutrophils), type II (associated with accumulated drug toxicity in hypersensitive persons), or type III (representing different etiologies induced by immune and toxic mechanisms). The pyrazolones (amidopyrine, dipyrone and butazones), phenothiazine derivatives, antithyroid drugs, and antibiotics are thought to be causative agents in agranulocytosis. The symptoms may involve sudden onset of high fever, sore throat with ulcerative angina, or stomatitis. Diagnosis of agranulocytosis is confirmed by severe granulocytopenia (0-0.5 X 10(9)/l), but bone marrow examination is required to rule out aplastic anemia and cancer. Treatment of drug-induced agranulocytosis involves immediate withdrawal of the incriminated drug. In most patients, granulocyte, reticulocyte, and thrombocyte cell counts overshoot in the regenerative phase of drug-induced agranulocytosis.