EURO-SHAKS, European study on HIV associated Kaposi's sarcoma, is a BIOMED 1 project financed by the European Union (DG XII). The Spanish side of the project has been financed by FISS (Fondo de Investigaciones Sanitarias). The aims of this study are to identify possible genetic, behavioural, biological and environmental risk factors for HIV associated Kaposi's sarcoma through a multicentre case-control study. An extensive personal questionnaire, a clinical data form and blood sample is required from all participants. In addition, a cutaneous biopsy is request from KS patients. The presence of several European groups in this project implies a large and diverse sample size and will allow to correlate the behaviour, clinical and biological data in different geographical areas, and therefore study the possible transmission routes as well as the natural history of the putative causal agent of KS. One of the main objectives of EURO-SHAKS is to create a European Bank of AIDS biological samples for possible future investigations.