The prognostic relevance of karyotype has been established in adult acute lymphoblastic leukaemia (ALL) patients treated with chemotherapy but not definitively evaluated in an allogeneic bone marrow transplantation (BMT) setting. To determine the factors affecting the outcome of allogeneic BMT for adults with precursor B-lineage ALL in first or second complete remission (CR), a total of 41 consecutive patients with a successful karyotype were enrolled in this study. There were 21 men and 20 women with a median age of 27 (15-43) years. The distribution of French-American-British (FAB) subtypes was as follows: L1 (n = 26), L2 (n = 15). Unfavourable karyotypes (n = 12) were defined as Ph+ or t(4;11). Disease status at the time of transplant was first CR (n = 35) or second CR (n = 6). With a median follow-up of 36 months, the 3-year probabilities of relapse and disease-free survival (DFS) were 36.3 +/- 8.4% and 57.3 +/- 8.4% respectively. Potential variables predicting worse relapse and DFS were FAB subtype (L2), extramedullary involvement, pre-BMT status (second CR), unfavourable karyotype and type of graft-versus-host disease (GVHD). Further multivariate analysis showed that karyotype and pre-BMT status were independently associated with relapse and DFS. In addition, chronic GVHD was found to be significantly associated with a lower relapse rate.