There is a threat that infectious diseases are becoming incurable as a result of a growing resistance from bacteria to antibiotics. Within Europe there is a considerable variation in resistance. Several studies suggest a causal relation between the use of antibiotics and the development of resistance and urge for a more restricted use of antibiotics. Most studies about the use of antibiotics focus on the prescribing physiscian. However, the use of antibiotics can also be the result of self-medication. The aim of this study is to assess the prevalence of self-medication and the attitudes that play a role in it. The study consist of two substudies: a survey among the population in general (N=3000) and a follow-up survey with interviews (N=100). The aim of substudy 1 is to assess the prevalence of self-medication with antibiotics in Europe. This cross-sectional study based on a mailed questionnaire, is part of a European project in which 22 countries are involved. The aim of substudy 2 is to explore opinions, attitudes and coping strategies. Based on the first substudy 100 persons will be selected and interviewed in 10 countries (among which Flanders in Belgium).