The causes of disqualification in a volunteer blood donor population for 2 yr were analyzed. Of 138,436 prospective volunteer blood donors, 24,327 (17.6%) donors were disqualified. Phlebotomy was unsuccessful in 721 (0.5%) donors and blood was drawn from 113,388 (81.9%) eligible donors. The majority of rejections were due to medical history findings (61.0% of all rejections). The 10 leading causes of disqualification were: low Hb/hematocrit, medication, allergies, signs and symptoms, high blood pressure, illness in last month, hepatitis and hepatitis exposure, malaria and travel overseas, atypical antibodies, and high serum bilirubin. Hepatitis B surface antigen was detected in 82 donors of 114,746 donors tested (0.07%).