We evaluated the efficacy and toxicity profiles of the combination of fludarabine, high-dose cytosine arabinoside (AraC), idarubicin, and granulocyte colony-stimulating factor (G-CSF) in refractory/relapsed acute myeloblastic leukemia (AML) patients. Between October 1998 and February 2002, 46 AML patients were treated with FLAG-IDA (fludarabine 30 mg/m(2), AraC 2 g/m(2) for 5 days, idarubicin 10 mg/m(2) for 3 days, and G-CSF 5 micro g/kg from day +6 until neutrophil recovery). Thirty patients were in relapse after conventional chemotherapy including cytarabine, etoposide, and daunorubicin or mitoxantrone according to the GIMEMA protocols. Four were in relapse after autologous peripheral stem cell transplantation and two after allogeneic bone marrow transplantation. Ten patients had refractory disease (after 10 days of standard doses of cytarabine, 3 days of mitoxantrone or daunorubicin, and 5 days of etoposide). Recovery of neutrophils and platelets required a median of 19 and 22 days from the start of therapy. Complete remission (CR) was obtained in 24 of 46 patients (52.1%) and 3 of 46 (6.6%) died during reinduction therapy: 2 due to cerebral hemorrhage and 1 due to fungemia ( Candida tropicalis). Fever >38.5 degrees C was observed in 40 of 46 patients (86.9%), 27 had fever of unknown origin (FUO) and 13 documented infections; 31 of 46 (67.3%) developed mucositis and 14 of 46 (30.4%) had grade 2 WHO transient liver toxicity. After achieving CR, 11 patients received allogeneic stem cell transplantation, 4 patients received autologous stem cell transplantation, 4 were judged unable to receive any further therapy, and 5 refused other therapy. Ten patients are at present in continuous CR after a median follow-up of 13 months (range: 4-24). In our experience, FLAG-IDA is a well-tolerated and effective regimen in relapsed/refractory AML. The toxicity is acceptable, enabling most patients to receive further treatment, including transplantation procedures.