Objective The aim of this study was to describe the prevalence of syphilis by geographical region and the frequency of behaviours and symptoms related to sexually transmitted diseases (STD).

Methods A cross-sectional study was performed with Brazilian conscripts in 2007. They answered a self-administered questionnaire on demographic issues, sexual practices, condom use and STD symptoms. They had a blood sample collected for a syphilis test.

Results A total of 35 460 conscripts answered the questionnaire and 75.5% reported previous sexual intercourse. Overall syphilis prevalence was 0.53% (95% CI 0.45% to 0.61%). By geographical region: northern (0.85%), northeast (0.82%), midwest (0.49%), southeast (0.34%) and southern region (0.26%). The final logistic regression model showed an association among having had syphilis and being 17 years old (OR 1.3; 95% CI 1.05 to 1.73), having up to 8 years of schooling (OR 1.5; 95% CI 1.03 to 2.22), living in the northern/northeast region (OR 1.2; 95% CI 1.04 to 1.36), being men who have sex with men (OR 4.5; 95% CI 2.59 to 7.81), reporting a previous history of STD (OR 2.7; 95% CI 1.03 to 6.99) and genital ulcers (OR 2.6; 95% CI 1.59 to 4.26).

Conclusions Addressing young people at the time of military enlistment may be a good time to consider new strategies for accessing and counselling this population, thus allowing the implementation of a more appropriate healthcare policy.