The hospital charts of 495 adult bone marrow (BM) donors to adult patients were reviewed to determine how necessary it is to collect autologous blood for marrow donation. An autologous transfusion was given to 79% of the donors. The median total volume of marrow harvested was 900 ml (range 450-1350 ml). The median number of nucleated cells harvested was 3.2 x 10(8)/kg patient weight (range 0.9-7.4 x 10(8)/kg patient weight). On the morning following the harvest, the median haemoglobin (Hb) concentrations were 104 g/l (79-135 g/l) in the female and 122 g/l (89-151 g/l) in the male donors autotransfused, and 96 g/l (75-127 g/l) in the female and 119 g/l (88-141 g/l) in the male donors not autotransfused. The post-donation Hb was lower than 85 g/l in four and lower than 90 g/l in 25 donors. Of the 25 donors with post-harvest Hb lower than 90 g/l, 23 were females and 14 had received an autologous transfusion. This study shows that, with a few exceptions, it is not necessary to collect autologous blood from healthy BM donors before the marrow harvest. The post-donation Hb concentrations do not decrease to levels detrimental to healthy persons whether autologous blood is transfused or not.