Background: Various countries require blood donor screening using assays applying specific HTLV–I and HTLV–II antigens. We evaluated the sensitivity and specificity of 4 anti–HTLV–I + II ELISAs (Abbott, Murex, Organon Teknika and Ortho). Methods: Panel A consisted of HTLV–I–positive individuals (n = 41), panel B of Mixed Titer Performance Panel 204 (Boston Biomedica Inc. panels C and D of dilution series from HTLV–I–positive (n= 30) and HTLV–II–positive (n =20) individuals and panel E of sera from first–time blood donors (n = 1,055). Results: In HTLV–I– and –II–positive samples, a sensitivity of 100% could be observed in all 4 ELISAs. In diluted HTLV–I– and –II–positive samples, probit analysis revealed that the Murex assay had the highest analytical sensitivity, followed by the ELISAs from Ortho, Abbott and Organon Teknika. In specimens from first–time donors, a specificity of 100% was observed in ELISAs from Murex, Organon Teknika and Ortho, and of 99.7% in the assay from Abbott. Conclusion: The 4 anti–HTLV–I + II ELISAs studied were appropriate as screening tests.