This phase II trial was performed to evaluate the efficacy of a new granulocyte colony-stimulating factor (G-CSF)-supported multi-agent chemotherapy protocol, LSG15, for aggressive adult T-cell leukaemia-lymphoma (ATL). Ninety-six previously untreated patients with aggressive ATL were enrolled and grouped as: acute type (58), lymphoma type (28) and unfavourable chronic type (10). Therapy consisted of seven cycles of VCAP (vincristine, cyclophosphamide, doxorubicin and prednisone), AMP (doxorubicin, ranimustine and prednisone) and VECP (vindesine, etoposide, carboplatin and prednisone). G-CSF was administered during the intervals between chemotherapy until neutrophil reconstitution was achieved. Eighty-one per cent of the 93 eligible patients responded [95% confidence interval (CI), 71·1–88·1%], with 33 patients obtaining complete response (35·5%) and 42 obtaining partial response (45·2%). The median survival time (MST) after registration was 13 months and the median follow-up duration of the 20 surviving patients was 4·2 years (range 2·8–5·6). Overall survival at 2 years was estimated to be 31·3% (95% CI, 22·0–40·5%). Grade 4 haematological toxicity of neutropenia and thrombocytopenia were observed in 65·3% and 52·6% of the patients respectively, but grade 4 non-haematological toxicity was observed in only one patient. LSG15 is feasible with mild non-haematological toxicity and improved the clinical outcome of ATL patients. MST and overall survival at 2 years were superior to those obtained by our previous trials.