Sensitivity and specificity of IgG detection by Western blotting performed with a lysate of Treponema pallidum whole cells were compared with those of the most common assays used in the laboratory diagnosis of syphilis, i.e. fluorescent treponemal antibody absorption test (FTA-ABS) and treponemal haemagglutination assay (TPHA). Thirty-five serum samples obtained from twenty-one patients with a clinical diagnosis of early syphilis, based on the presence of typical chancre or skin or mucous membrane lesions, were studied. In addition, thirty blood samples from donors, ten sera positive for Borrelia burgdorferi and five positive for Leptospira interrogans were tested as controls. The clinical diagnosis was the reference method used to compare the performance of the serological tests. Western blotting performed with a sensitivity and specificity of 100%, whereas the corresponding sensitivity and specificity for FTA-ABS were 88.5% and 98%, respectively. The performance of TPHA showed a sensitivity of 86% and a specificity of 100%.