We conducted a prospective study using an anonymous questionnaire and semistructured interviews on 60 patients with HIV to assess the psychological and socioenvironmental factors that may result in risk-taking behaviour. The patients were mainly young males (mean age 33.1 +/- 7.0 years) (sex ratio 2.3) deprived in both social and educational terms. Injecting drug use was the predominant risk factor and was characteristic of a first group of young men raised in large families shattered by rural-urban migration, with an antisocial personality. A second group consisted of women, mostly illiterate from traditional rural settings. They had been infected by their spouses who had worked abroad, whether drug users or not. Approaches for the prevention of HIV infection are proposed.