As a part of an assessment of the Swiss drug harm-reduction policy, cross-sectional surveys were conducted in 1994, 1996 and 2000 among attenders of all needle exchange programmes (NEP) in Switzerland to assess changes in specific aspects of their health related to drug use. Data were gathered in each NEP over one week, using a questionnaire completed partly with an interviewer and partly self administered. The questionnaire covered socio-demographic characteristics, drug consumption, risk, prevention behaviour and state of health. Over a 6-year period (1994-2000), the average age of NEP attenders rose by 4 years. The prevalence of reported HIV remained fairly stable at around 10%. Reported level of Hepatitis C prevalence was high (59%). Incidence of used injection equipment sharing during the last 6 months was low and stable (9% in 1994, 12% in 2000); however, other forms of risk behaviour linked to intravenous drug use, such as sharing spoons, cotton or water, were more frequently reported. The HIV epidemic among NEP attenders seems to be contained, but this is not the case with Hepatitis C, and more attention should be paid to its prevention.