Analysis of individual data captured within the framework of the Swiss HIV Cohort Study (see http://www.shcs.ch). Based upon prospectively collected clinical information and interviewer administered questionnaires on sexual behaviour. For the survey on HIV infected patients not included in the SHCS, we collected aggregrate information from the participating clinics and private practices. Method: Standardised analysis of content, Standardised analysis of documents, Participant observation, Observation without participation, Standardised interviews face-to-face, Secondary analysis of individual data, Secondary analysis of aggregate data Also see: Cohort profile: the Swiss HIV Cohort study. Swiss HIV Cohort Study, Schoeni-Affolter F, Ledergerber B, Rickenbach M, Rudin C, Günthard HF, Telenti A, Furrer H, Yerly S, Francioli P. Int J Epidemiol. 2010 Oct;39(5):1179-89. PMID:19948780 The Swiss HIV Cohort Study: rationale, organization and selected baseline characteristics. Ledergerber B, von Overbeck J, Egger M, Lüthy R. Soz Praventivmed. 1994;39(6):387-94. PMID:7817627