A combined immunoassay for the simultaneous detection of antibodies to HIV-1/2 and HTLV-I/II (Bioelisa, Launch Diagnostics) has been evaluated to determine its suitability for routine use in blood screening. 84,222 donations were tested from 76,452 donors. One HIV- and 1 HTLV-1-positive donor were identified. The specificity was 99.7%, and the sensitivity for anti-HIV-1, anti-HIV-2, and anti-HTLV-1 on 173 positive sera was 100%; 2 of 25 anti-HTLV-II-positive sera were non-reactive. Although the specificity of the assay is not as high as that of HIV-1/2 kits currently in UK transfusion use, the information gained about donor HTLV antibody status makes the test an attractive alternative to them.