Summary points : Trend data show that the numbers of new diagnoses of sexually acquired HIV infections increased by 20% in western Europe between 1995 and 2000. Gonorrhoea reports have increased in France, the Netherlands, Sweden, Switzerland, and the United Kingdom. The Netherlands, France, Ireland, and the United Kingdom reported outbreaks of syphilis in men having sex with men, including men already infected with HIV. These preliminary data for several European countries imply that people may increasingly take sexual risks. HIV remains Europe's most important sexually transmitted infection, yet complacency over HIV prevention may have set in among individuals, populations, and some governments in western Europe.