Ten years experience of 14 hospitals in Kanto district with drug induced blood dyscrasia (DBD) were reviewed. There were 78 patients, male/female ratio was 1:1, and cases more than 80 years old were 10.3%. It was very difficult to identify the causative agents, and only 8 cases were definitive. After disease 9 case were died, and DBD prolonged more than 50 days from onset in 8 patients. Thirty-one patients (39.7%) were due to Antibiotics, beta-lactam were most frequent, 12 cases were due to analgesics, 5 patients were due to thiamazole. In order to elucidate the incidence of DBD, studies had carried out concerning antibiotics and H2 receptor antagonists (H2RA). DBD due to antibiotics increased from 0.5% in 1981 to 4.2% in 1982, because medication of third-generation cephalosporins was began to use. In 109 outpatients with H2RA, there was no DBD, but in 54 hospitalized patients DBD were found in 3.6%. DBD might be more frequent in fact. It is necessary to start big study and to develop new technique for confirmation.