Introduction The promotion of HIV prevention among homosexual men is certainly one of the most successful health campaigns to be instituted over the last several decades. However, in spite of the impressive success of interventions targeted to this population, prevention efforts have not been as effective as was hoped. This is not seen so much in the annual rate of new infections in Germany, which has stabilised (see Marcus, Chapter 3), but rather in the relatively constant level of risk contacts in certain contexts of homosexual life. Prevention efforts for homosexual men were clearly most successful precisely where they were predicted to fail; namely, in relation to casual sexual contacts. HIV prevention has enjoyed less success, however, in the context of steady relationships between men. On the basis of the empirical data gathered to date, one could characterise the development of a committed relationship between men as a situation which promotes risk behaviour, thereby making the individuals involved more susceptible to an HIV infection. Ironically, love has turned out to be a risk factor (Dannecker, 1990; Davies et al. 1993; Schiltz and Adam, 1995; Bochow, 1997).