To develop new strategies aimed to reduce the delay in seeking HIV diagnosis, we proposed to identify correlates of late diagnosis of HIV infection in France. Late testing was studied among the 1077 patients diagnosed from 1996 and enrolled in the ANRS-EN12-VESPA, a representative sample of the French HIV-infected population. Patients were defined as 'late testers' if they had presented either clinical AIDS events or CD4 cell count <200/mm(3) at diagnosis. In all, 33.1% were classified as late testers, among whom 42.6% had discovered their HIV infection at the time of AIDS events. This proportion increased with age and was higher for heterosexual men and migrants. Among the non-migrants heterosexual population, late diagnosis was more frequent among people in longstanding couple, with children and conversely was less likely among individuals with large number of sexual partners. Being on welfare benefit before diagnosis was associated with a lower risk of late diagnosis. Among migrants, lack of recent steady partnership was associated with an increased risk, as being diagnosed during the first year of stay in France. Our results showed low risk factors of infection were risk factors of late testing. Public communication should aim at improving the awareness of HIV risk in longstanding couples with stable employment, both among homosexual and heterosexual populations. Among migrants, HIV testing with informed consent short after entry should be improved, especially towards individuals not in couple.