We studied the expression of gelatinase-A (MMP-2) and gelatinase-B (MMP-9) in bone marrow aspirates from 54 patients with leukaemia. Specific staining patterns for different leukaemia subtypes are described. Most intresting were findings in acute myeloid leukaemia (AML), where MMP-2 staining correlated strongly with prognosis. Three year event-free survival after conventional treatment for patients with MMP-2 positive blast cells was 82%, while all the conventionally treated patients with MMP-2 negative blasts relapsed within 13.5 months. After treatment with allogeneic bone marrow transplantation, 3-year event-free survivals were 100% and 80% for MMP-2 positive and negative patients respectively.