Forty cases of drug-induced agranulocytosis from the Department of Medicine, Faculty of Medicine, Chiang Mai University during the 12 year period 1975-1987 were analysed. In 32 cases, the related etiologic drugs were identified. These were thiacetazone and isoniazid in 10 cases (25%), propylthiouracil in 6 cases (15%) sulfa drugs in 5 cases (12.5%) combination of analgesic and antibiotics in 3 cases (7.5%), anti-psychotic in 2 cases (5%), antibiotics in 5 cases including, ampicillin (2 cases) and others (3 cases), and ether in 1 case (2.5%). The other 8 cases (20%) received unknown drugs from private clinics. Twenty-four cases had complete recovery in 13-14 days after withdrawal of the incriminating drugs, and sixteen cases (40%) died with septicemia.