The laboratory and clinical experience of a single institution of 75 consecutive children undergoing bone marrow harvesting, 65 for subsequent autologous reinfusion and 10 for allogeneic infusion, was analysed and compared in detail with the adult literature. The median age was 9.3 years (range 6 months-20 years) with equal distribution between all childhood age groups. The median volume of marrow harvested was 15.94 ml/kg (range 4.94-27.7 ml/kg) and there was no significant difference within each age group. Fifty percent of autologous marrows (32/65) required Ficoll-Hypaque density separation and the other 50% (33/65) were separated by using the Cobe 2991 cell separator. Allogeneic harvests yielded 5.1 x 10(8) cells/kg vs 2.4 x 10(8) cells/kg for autologous harvests. Only 48% of children required red cell transfusions following this procedure (average volume 9.36 ml/kg). There were no episodes of postoperative fever or infection. There was only one episode of life-threatening morbidity (1.3%), a pulmonary embolus related to venous stasis from tumor obstruction. Lastly, the average time to engraftment following autologous reinfusion (n = 10) (neutrophils greater than or equal to greater than or equal to 500 x 10(6)/l for 2 days) was 19.8 +/- 5.3 (SD) days and time to platelet recovery (greater than or equal to 20 x 10(8)/l without transfusions) was 25.6 +/- 5.8 days. This study suggests that bone marrow harvesting in a large cohort of children with an active pediatric malignancy for a future autologous bone marrow transplantation is a safe and reliable procedure with a low incidence of serious morbidity.