IN NO FIELD has medical opinion reversed itself so completely as in that of blood letting versus blood replacement. A short time ago while visiting the reconstructed colonial town of Williamsburg, one saw the tools of the old barber surgeons. A copy of a manuscript on the wall stated that George Washington was bled on several occasions during his terminal illness, without seeming benefit. In this paper, I would like to emphasize some of the ills of blood replacement rather than withdrawal. Due to the impetus given by life-saving transfusions during the war, blood transfusion has become universally available in all parts of the country. This has not proved an unmixed blessing, however, for the dangers associated with blood transfusion have also been greatly multiplied thereby. The factors which give rise to these dangers are as follows: 1) those associated with donor; 2) those associated with stored blood; 3) those associated with act of transfusion; 4) those associated with recipient. 1. Factors Associated with Donor 1. Homologous serum jaundice. 2. Allergic reactions. 3. Transmission of tropical and other infections. The danger of transmitting the virus which causes jaundice is greater than may be realized, and is rebated to the incidence of the carrier state in the population. The incidence in the general population has been estimated as from 0.1% to 0.5% to 0.35%. In one Army Camp in the United States it was found to be as high as 5%. As one might expect the danger of transmission is greatest the more recently the donor has had jaundice, but some work in Germany suggests that even 6 years or more after having hepatitis, donors may transmit the virus to 3.6% of recipients.