We evaluated the effect of granulocyte colony-stimulating factor (G-CSF) on the median survival of 17 patients with Adult T-cell leukemia (ATL). Standard-dose combination chemotherapy using the response-oriented cyclic multidrug (RCM) protocol with G-CSF (lenograstim 2 microg/kg/day or filgrastim 50 microg/m2/day) was administered between October 1990 and December 1994. Complete responses (CR) were achieved in 11 (64.7%) patients, and partial responses (PR) in 4 (23.5%) patients. The median duration of survival was 7.4 months, compared with 6.0 months in ATL patients treated with the RCM protocol alone (historical controls) (n.s.). Infectious complications were the cause of death in 4 (26.7%) of the 15 patients who died. The median duration of neutropenia (absolute neutrophil count < 1.0 x 10(9)/L) was 6 days. G-CSF, in the doses and schedules used here, may have shortened the duration of neutropenia and reduced the incidence of fatal infectious complications. However, concomitant use of G-CSF did not prolong the median duration of survival in patients with ATL treated according to the RCM protocol.