We analyzed the incidence and prognosis of bacteremia/fungemia and pneumonia during remission induction therapy of a newly diagnosed acute myelogenous leukemia (AML) in the Japan Adult Leukemia Study Group treated with individual protocols of AML-87/-89 (1987-1991), AML-92 (1992-1995), AML-95 (1995-1997), and AML-97 (1997-2001). Bacteremia/fungemia was present in 251 of 2585 cases (9.7%); the causative microorganism was gram-positive bacteria (GPB) in 122 cases (49%), gram-negative bacteria (GNB) in 90 cases (36%), fungi (F) in 31 cases (12%), and polymicrobes (P) in 8 cases (3%). Particularly prevalent were Pseudomonas aeruginosa in 49 cases (20%), Staphylococcus epidermidis in 29 cases (12%), and Staphylococcus aureus in 25 cases (10%). With AML-87/-89, incidence of bacteremia/fungemia was 11.8% while it was 9.4% with AML-92, 8.7% with AML-95, and 9.2% with AML-97. The proportion of GPB, GNB, F, and P was 40, 41, 16, and 3% in AML-87/-89, 46, 40, 11, and 3% in AML-92, 48, 39, 11, and 2% in AML-95, and 59, 26, 11, and 4% in AML-97. The mortality rate by period was 26.5, 16.4, 14.0, and 6.8%, respectively. Pneumonia was found in 433 cases (16.8%); microbiological research covered 359 cases of AML-87/-89, AML-92, AML-97 and excluded AML-95 as there was no listing for the causative microorganism on questionnaires. Microbiologically documented pneumonia was found in 123 cases (34.3%), with GPB in 33 cases (27%), GNB in 28 cases (23%), F in 44 cases (36%), and P in 18 cases (15%); particularly prevalent were Aspergillus in 23 cases (19%), Staphylococcus aureus in 16 cases (13%), and Pseudomonas aeruginosa in 15 cases (12%). The incidence of pneumonia overall was 24.6% with AML-87/-89, 16.9% with AML-92, 13.9% with AML-95, and 12.9% with AML-97, with a mortality rate of 28.9, 33.3, 16.7, and 16.7%, respectively. Incidence of bacteremia/fungemia and pneumonia complicating AML has tended to decline in recent years, and mortality has also tended to improve.