Herpes simplex virus type 2 (HSV-2) is the dominant primary causative agent in genital ulcerative infections. Since infections with HSV-2 usually are acquired through sexual contacts, antibodies are rarely found before the age of onset of sexual activity. Although most genital infections are caused by HSV-2, a rising proportion has become attributable to primary type 1 herpes simplex virus (HSV-1) infection. Genital HSV-1 infections are usually both less severe clinically and less prone to recur. HSV-1 infection might render a certain protection against an HSV-2 infection and seems to mitigate the HSV-2 illness. It is not yet clear whether the advent of HSV-1 genitally will reduce the general occurrence of HSV-2. Increased efforts to protect against sexual transmission of the herpes viruses should have an effect on the transmission of other chronic diseases, such as the human immunodeficiency virus (HIV). In conclusion, it seems that increased sexual promiscuity and more advanced sexual techniques contribute to an unnecessary rise in prevalence of genital HSV infections, thus also affecting transmission of other genitally manifested diseases in targeted populations.