Prognostic factors for survival following allogeneic BMT for AML include age, disease status and cytogenetic risk classification. Lactate dehydrogenase (LDH) levels have not been studied as a potential risk factor. We reviewed our experience with BMT for AML and included LDH at the time of admission in an analysis of prognostic factors for survival. We found that LDH >330 U/l (1.5 times the upper limit of normal at our institution), older age, active disease, peripheral stem cell graft and male-to-male transplant were significant adverse predictors of survival. After accounting for LDH, other factors such as disease status and cytogenetics were not significantly associated with the outcome of BMT. All but one patient with an LDH >330 U/l had active disease. However, when patients in CR were excluded, LDH >330 U/l remained a significant adverse predictor of overall survival (hazard ratio 2.70, 95% confidence interval 1.41-5.16, P=0.003). We conclude that LDH is an important adverse risk factor for survival and should be included in future studies of risk performed on larger patient cohorts.