One of the major obstacles to the eradication of perinatal transmission of syphilis is the delay in obtaining the results of syphilis serological tests. The availability of on-site syphilis testing lead to this study which attempted to evaluate on-site syphilis testing performed by nursing staff. The seroprevalence of syphilis by laboratory rapid plasma reagin (RPR) was 8.2% (n=42). Twenty-one of the 42 women were correctly identified by the on-site test. The overall sensitivity of on-site testing was 50% [95% confidence interval (CI)=34.4-65.6]; specificity of 90.9% (95% CI=87.8-93.2). The on-site test correctly identified as uninfected 429 of the 471 women reported as RPR negative by the laboratory, giving a specificity of 91.1% (95% CI=88.1-93.4). The results of the study show that on-site RPR test had a sensitivity of 75% in respect of the clinically important titres of > or = 1:8. The specificity of the on-site test was 91.1% and on-site testing only failed to detect syphilis in those patients with titres of 1:1 and 1:2. On-site testing is a practical and cost-effective option to prevent congenital syphilis, in settings of a high prevalence of syphilis and using skilled testers.