We studied the long-term outcome of 136 adults with acute leukemia (age 15-48 years at transplant, median 28; 112 myeloid, 22 lymphoblastic, 2 undifferentiated) who were alive in continuous remission two years after allografting from HLA-identical sibling donors. Six relapsed 25-46 months (median 30) after BMT. Fourteen (10%) died of non-relapse causes (12 transplant-related and 2 unrelated) 24-140 months (median 73) after BMT; mainly due to complications of chronic GVHD (8 infections, 3 secondary malignancies). One hundred and seventeen (86%) patients are alive in remission 25-226 months (median 103) after BMT; 116 (85%) in continuous remission. Eight survivors have symptomatic chronic GVHD requiring therapy (Karnofsky scores 60-90%, median 80%). The majority of those without chronic GVHD have Karnofsky scores of 100%. The 10-year probabilities of survival, toxic death, and relapse (from the 2-year mark) are 81%, 13%, and 5%. Twenty-two (19%) survivors had creatinine levels of > 110 mu mol/L tone more than double), and 11 (9%) had bilirubin levels of > 17 mmol/L tone more than double) at the last follow-up. The absence of chronic GVHD at the 2-year mark OCR 3.5, P=.004), and female sex (RR 2.9, P=.04) influenced overall survival favorably, and the absence of chronic GVHD at the 2-year mark (RR 8.1, P=.001) influenced toxic death favorably. We conclude that patients with acute leukemia who are alive and well without chronic GVHD two years following an allograft have a high probability of being cured, whereas patients with active chronic GVHD requiring immunosuppression continue to be at risk of non-relapse death. The incidence of long-term liver and kidney dysfunction measured by serum bilirubin and creatinine is low.