HIV-1 antibody determination by ELISA screening takes 4 hr to complete and is not reliable. Regular Western blot can take up to 24 hr. This makes organ transplantation both difficult and risky with regard to HIV-1 transmission. We developed a modification of the Western blot technique that takes under 50 min, is transportable, is definitive on site, and does not delay organ retrieval. This test has been called the Quick Western Blot. We examined 459 serum specimens from referrals; from the AIDS Testing Proficiency Panel, Walter Reed Army Institute of Research; and from 36 organ donors. All specimens were tested by ELISA HIV-1 Ab screening, the regular Western blot, and by the Quick Western Blot. The organ donors were initially tested on-site during organ procurement by the Quick Western Blot and later had complete testing by the reference methods. Compared with regular Western blot, the ELISA showed a specificity of 78.4% and a positive predictive value of 65.5%, whereas the Quick Western Blot was as reliable and specific as the regular Western blot, but much quicker. Because of the rapidity and specificity of the test, this test has particular utility in the screening of organ donors, as was shown in a case of multiple organ donation where the ELISA was negative, but the Quick Western Blot was found positive and thereby prevented the donation of HIV-1 infected organs.