In order to investigate the prevalence of HIV infection among Greek intravenous drug users (IVDU), its trend during years recent and possible risk factors, we studied 893 inmates recently admitted to the main prisons of Greece from 1986 to 1989. Screening and counselling was offered to all of them, The acceptance rate was 98%. One thousand one hundred and two IVDUs voluntarily attending the AIDS Reference Centre in Athens for counselling and screening were also included in the study. Anti-H1V were determined by commercially available radioimmunoassays, and positive results were confirmed by Western Blot. Our results showed that the prevalence of HIV infection remained very low in both groups during the study period; it was similar to the prevalence found (2.1%) in stored sera drawn in 1982 from imprisoned IVDU. In the non-prisoner group, the prevalence among those who reported needle/syringe sharing (2.6%) was similar to that among those who denied sharing (2.5%). This lack of difference may be due to the fact that sharing is only an occasional practice and that cleaning of the injection equipment is common. We conclude that the prevalence of anti-HIV in IVDU in Greece is considerably lower than that in neighbouring countries and that it has remained stable during the last eight years. Further studies are necessary to identify behavioural and other risk factors.