The association between red blood cell transfusions and infectious complications in 484 patients with acute injuries was studied in 1989. The median age was 62 years (0.5-97) and the median stay 7 days (3-141). Infectious complications developed in 46 (9.5%) patients. A number of potential risk factors, except blood transfusion, were analyzed in a logistic regression model to determine significant predictors of infectious complications. Blood transfusion as a cofactor was then added to this model. The final logistic regression analysis showed a relationship between blood transfusions and infectious morbidity that was independent of the other significant factors; Injury Severity Score, age, and surgical procedure. The corrected odds ratios for infection were 1.6 (95% confidence interval: 0.7-3.7) when 1-4 units of blood were given and 6.4 (95% CI: 2.3-18.3) when more than 4 units were used.