The aim of this study was to evaluate the outcomes for Philadelphia-chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL) patients in remission treated with allogeneic bone marrow transplantation (BMT). Twenty-three adults were entered onto this study. The 2-year probabilities of relapse and disease-free survival (DFS) were 39.4 +/- 11.6% and 43.5 +/- 10.3% respectively. The presence of chronic graft-versus-host disease (GVHD) was found to be an independent predictive factor affecting lower relapse and DFS. To monitor the BCR-ABL transcript, we also analysed 48 bone marrow samples of eight patients using real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR). The kinetics of the BCR-ABL transcript correlated well with the patients' clinical course. In six patients who were in continuous remission after BMT, a rapid decrease in BCR-ABL copy number to the PCR-negative status was observed after the development of chronic GVHD. Meanwhile, routine bone marrow examination of two patients showed PCR positivity with a 3 or 4-log increase of BCR-ABL copy number and subsequent haematological relapse, which occurred 2 and 4 months later respectively. Although our data should be interpreted cautiously, the presence of chronic GVHD may reduce the risk of relapse in Ph+ ALL. Real-time quantitative RT-PCR appears to be a useful test for BCR-ABL transcript monitoring.