The prognostic value of diagnosis-remission interval on leukemia-free survival (LFS) after bone marrow transplantation (BMT) was investigated retrospectively in 193 adult patients with acute lymphoblastic leukemia (ALL) transplanted in first remission and reported to the EBMT between 1979 and 1986. Patients achieving remission within 8 weeks of diagnosis ('fast responders') had better LFS after BMT than those with remission after 8 weeks ('slow responders'): LFS at 3 years was 43% vs 32% for fast and slow responders, respectively (p = 0.04). The effect on LFS was particularly severe for slow responders transplanted within 3 months of remission. Only 17% of the slow responders with short remission-BMT interval survived at 3 years. Decreased LFS was caused by both excess of transplant-related mortality and increased relapse incidence. In a multivariate analysis, time intervals (both diagnosis-remission and remission-BMT) were the strongest independent prognostic factor for LFS, probability of relapse and transplant-related mortality. We conclude that the intervals diagnosis-remission and remission-BMT have a strong prognostic value in adult patients with ALL not only for remission duration after conventional treatment, but also for LFS after BMT.