Nowadays, sex education contributes to public health not only with regard to the prevention of HIV/AIDS, other sexually transmitted infections and sex abuse, but it is also concerned with addressing aspects such as interpersonal relationships and psychosocial implications. The school setting has emerged as a unique environment for access to information and scientific knowledge that contribute to better understanding of the various dimensions of sexuality. Teachers' and future teachers' conceptions about sex education are analysed in this paper. Data were obtained from a questionnaire designed by the European Biohead-Citizen research project. Responses were received from 2 537 teachers from four Mediterranean countries (Tunisia, Lebanon, Morocco and France) who completed the questionnaire. The methodology is based upon analyses of core components that support the discovery of teachers' conceptions. Following that exercise, standardised factorial scores were calculated. Results for in-service and pre-service teachers show high correlations between their conceptions and national culture, religious beliefs, and level of academic training. Detailed results are presented and discussed.