The micro HCT‐PCT method and the CuSO4—VDRL method were compared in the screening of 10,598 consecutive blood donors. The more accurate micro HCT at 40 to 60 per cent limits (13.5 Gm. per cent minimum Hgb.) rejected 4 per cent of the donors as compared to 2.9 per cent with CuSO4at the 12.5 Gm. per cent Hgb. level. Based on an earlier study comparing the CuSO4method at the 12.5 and 13.5 Gm. per cent levels in over 7,000 donors, the rate at 13.5 Gm. per cent would have been 3.2 per cent. The reasons for the difference between the two test methods are presented. The opportunity to inspect the plasma resulted in the advance rejection of 454 donors (4.3%) for excessive chyle, six for apparent icterus, and one for abnormal buffy coat. The rate of positive serology was 2.2 per cent with the PCT test, again permitting advance rejection, as compared to a rate of 1.7 per cent with the VDRL, which is done after donation. There were nine negative PCT tests which were positive with the VDRL during a period of technical difficulties with outside diameter variation in the special PCT capillaries, eight of which were confirmed as false positive VDRL results. There were no negative PCT tests with positive VDRL results after this problem was corrected. The HCT‐PCT method of donor screening should be substituted for the CuSO4—VDRL method because it provides a better quality of donor screening through a more accurate measure of red cell normalcy and advance rejection of donors with excessive chyle, icteric plasma, abnormal buffy coat or hematocrit, as well as those with a positive serology. This advantage is greatly enhanced, since use of the method results in a savings in operating costs of over 6 per cent, through the advance rejection of donors whose blood would have been u