Routine sterility control of a unit of leukocyte-depleted erythrocyte concentrate yielded growth of Yersinia enterocolitica serotype O:3. Plasma of the donor showed a high titer of agglutinins against the homologous organism. Although the donor was apparently well at the time of donation, he had a history of protracted terminal ileitis treated by surgery. The recipient of the contaminated blood was taking broad-spectrum antibiotics and did not experience any adverse effect. Fourteen other cases of transfusion-associated yersiniosis have been reported.