Patients with chronic granulocytic leukemia (CGL) can be classified in different groups according to risk factors at diagnosis (Sokal). The aim of the present study was to assess the impact of Sokal's risk factors in 100 patients with CGL undergoing allogeneic BMT. Patients were in first chronic phase (CP) (n = 65), or with advanced disease (n = 35), grafted from an HLA-identical sibling following conditioning with cyclophosphamide and total body irradiation (TBI). Median follow up for survivors is 1783 days (429-3533 days). Variables recorded at diagnosis to calculate Sokal's prognostic index were: leukocyte, platelet and peripheral blood blast cell counts, age and spleen volume. The median value of the Sokal index was 0.87. Projected survival for all patients at 9 years was 28% (95% confidence limits (CL) 6-49), 48% (34-62) for first CP patients and 15% (0-36) for more than first CP patients (p = 0.04). Survival was 25% and 31% for all patients with a Sokal index of < 0.87/> or = (p = 0.07) and 55% vs 39% for first CP patients only (p = 0.03). The relapse rate was similar for patients with Sokal index < 0.87/> or = (41% vs 39%, p = 0.9) and this was also true for first CP patients (33% vs 26%, p = 0.8). In multivariate analysis, an interval between diagnosis and BMT of > 2 years was the most significant negative predictor for survival for the whole group of patients (p = 0.01) and more so for first CP patients (p = 0.0004).(ABSTRACT TRUNCATED AT 250 WORDS)