More than 410,000 people participated in the National Marrow Donor Program (NMDP) as of October 1, 1991, and more than 850 volunteers had donated marrow. While the incidence of serious morbidity as a result of bone marrow donation is rare, the incidence of lesser complications and the long-term consequences of marrow donation are not known. To determine the incidence of donor complications and measure the recovery time of volunteer, unrelated marrow donors, we analyzed the results of surveys of the first 493 persons who donated marrow through the NMDP. The marrows were collected at 42 centers. The median age of the donors was 37.9 years (range 19.1 to 55.6 years). The median volume of marrow collected was 1,050 mL (range 180 to 2,983 mL). Autologous red blood cells were transfused to 89.8% (439) of donors but only 0.6% (3) of donors received allogeneic blood. Acute complications related to the collection procedure occurred in 5.9% of donors; but a serious complication, apnea during anesthesia, occurred in only one donor. When donors were questioned approximately 2 days following discharge from their hospitalization, most donors described symptoms related to the collection; 74.8% experienced tiredness, 67.8% experienced pain at the marrow collection site, and 51.6% of the donors experienced low back pain. Donors were surveyed repeatedly until they felt that they had recovered completely. Mean recovery time was 15.8 days; however, 42 (10%) donors felt that it took them > or = 30 days to recover fully. The duration of the marrow collection procedure and duration of anesthesia both positively correlated with donor pain and/or fatigue following the collection; but the duration of the collection procedure had the highest correlation with post-collection pain and fatigue. The volume of marrow collected per unit of donor weight was more weakly correlated with donor pain and/or fatigue than the anesthesia and collection times. When multivariate analysis was used to analyze the correlation between donor recovery time and these variables, only the duration of the collection was found to correlate significantly with donor recovery time (P = .001). This analysis demonstrates that marrow donation is well tolerated with few complications. To decrease further the incidence of donor discomfort and recovery time following donation, the duration of the collection procedure, and probably the duration of anesthesia, and the volume of marrow collected, should be kept to a minimum.