A sentinel surveillance system for the control of sexually transmitted diseases (STD) among foreigners was developed in Italy in 1991. From January 1991 to June 1995, 4030 foreigners with a new STD episode were reported. More than one-third of them were North-Africans. The most frequent STDs were non-specific urethritis and genital warts among men, and non-specific vaginitis and latent syphilis among women. The overall HIV prevalence was 5%, with large differences in rates in people from different continents. Very high HIV-positivity rates were observed among homosexuals and homosexual IDUs from Central-South America, with 39.1% and 77.8% seropositive individuals respectively. These data stress the need for increased knowledge of both the spread of risk factors for STDs among immigrants. Particular attention should be paid to counselling procedures focused on the prevention of risk behaviours for acquiring STDs and HIV infection.