Factors which may influence haematopoietic recovery after allogeneic bone marrow transplantation were analysed. Forty-six evaluable patients transplanted with lymphocyte-depleted marrow for acute lymphoblastic leukaemia, acute non-lymphoblastic leukaemia, chronic myeloid leukaemia, myelodysplastic syndrome and severe aplastic anaemia were studied. The median time for platelet recovery to greater than or equal to 20 and to greater than or equal to 50 x 10(9)/l was 21 (9-72) and 26 (11-86) days respectively. The neutrophil recovery to greater than or equal to 0.5 x 10(9)/l and the leucocyte recovery to greater than or equal to 1.0 x 10(9)/l was 19 (8-47) and 18 (6-47) days respectively. No relation was found between the number of infused granulocyte-macrophage colony-forming cells, erythroid burst-forming cells, diagnosis, graft-versus-host disease, antibiotic administration and recovery. Addition of a continuous 6-day infusion of anthracyclines to the conditioning regimen delayed the median recovery of platelets, neutrophils and leucocytes by 7-9 days. Fever during aplasia also inhibited haematopoietic recovery. It is speculated that leakage of intracellular anthracyclines after bone marrow infusion or fever secondary to anthracyclines-induced oromucositis is responsible for the delayed bone marrow recovery.