It is well established that transfusions given prior to transplantation diminish rejection, and recent reports suggest that transfused patients having surgery for cancer developed more metastases than those who did not receive transfusions. To our knowledge, however, there are no studies evaluating whether transfusions result in increased rates of infections. To investigate this, 295 Lewis rats were subjected to a 25% total body surface area burn and were given either 3 mL of Lewis blood, 3 mL of A'Solagoft Cancer Institute rat blood, or 9 mL of lactated Ringers' solution intravenously on day 1 before burn or on the day of burn. One additional group received 1-mL transfusions on days 9, 7, and 5 before burn. The burns were painted with 1 X 10(8) Pseudomonas aeruginosa lot No. 1244 on postburn days 0, 1, or 2. All rats were followed up for 28 days and survival and mean survival times were recorded. Transfusion of A'Solagoft Cancer Institute blood increased mortality unless given within 24 hours prior to Pseudomonas challenge, when it diminished mortality. Transfusion with syngenic Lewis blood had no effect. We conclude that transfusions may adversely affect survival when given before bacterial challenge, possibly due to immunosuppression from exposure to non-self-histocompatibility antigens.