Travel to tropical countries is an important factor in the spread of sexually transmitted diseases. In spite of intensive anti-AIDS campaigns, some 30% of Swiss tourists have casual sexual contacts abroad. The prevalence of sexually transmitted diseases is higher in tropical countries than in western industrialized countries. More than 25% of cases of gonorrhea treated in Switzerland from 1989-1991 were imported from abroad. The penicillin producing Neisseria gonorrhoeae strains (PPNG) isolated in Switzerland from 1989-1991 are mainly imported from abroad (60%). The typical "imported sexually transmitted diseases" in Switzerland are chancroid, lymphogranuloma venereum and donovanosis. The clinical manifestations, laboratory and special examinations, and treatment of these diseases are described. The most frequent sexually transmitted disease from the so-called "imported tropical STD's" is chancroid. Chancroid is also a major risk factor for HIV infection.