The specimen of choice for transfusion service testing traditionally has been serum. We investigated the use of ethylenediaminetetraacetic acid (EDTA) plasma as an alternative to serum, because the use of potentiating media, along with anti-IgG antiserum, has eliminated the need for complement in the sample. The advantages of plasma use include expediting testing in emergencies and in samples with clotting problems, and eliminating the need for EDTA-suspended donor cells for detection of potent anti-A and anti-B. Also, EDTA samples are used for accurate direct antiglobulin testing, and some transfusion services use EDTA tubes for the ABO and Rh. A single tube for all testing would simplify specimen identification and be cost effective.