OBJECTIVES: To describe sexual and HIV/sexually transmitted infection (STI) risk behaviours in Slovenia. METHODS: A nationally representative cross-sectional survey of the general population aged 18-49 years in 1999-2001 was conducted. The data were collected by face-to-face interviews and anonymous self-administered questionnaires. Statistical methods for complex survey data were used. RESULTS: 849 men and 903 women were interviewed. In the past 5 years, both men and women reported a median of one heterosexual partner (means 3.2, 1.5, respectively), concurrent heterosexual partnerships were reported by 24.4% of men and 8.2% of women, heterosexual sex with non-Slovenian partners by 12.6% of men and 12.2% of women, forced sex by 4.8% of women, paid heterosexual sex by 2.6% of men, sex with another man by 0.6% of men and heterosexual sex with an injecting drug user by 1.2% of men and 1.3% of women. In the past year, 22.7% of men and 9.5% of women reported forming at least one new heterosexual partnership. The mean numbers of episodes of heterosexual sex in the previous 4 weeks were 6.1 for men and 6.0 for women. Consistent and inconsistent condom use was reported more frequently among men reporting multiple female partners and those not married or cohabiting. CONCLUSIONS: Recent patterns of reported sexual behaviour are consistent with a low risk of HIV and STI transmission in Slovenia. The results will inform Slovenian sexual health policies including HIV/STI prevention, and are particularly valuable because population-based data on HIV/STI risk behaviour have not previously been available in low HIV prevalence countries of central Europe.