In the past decade, there have been dramatic changes in Mexico in public opinion and support for sexuality education. The growing recognition that young people are sexually active before marriage and need information in order to make responsible choices is the result of intensive health promotion efforts by public and private entities. This paper is about the work of a Mexican non-governmental organisation, IMIFAP, which has designed and evaluated sexuality education programmes for children from pre-school age through adolescence and for their parents, based on formative research. IMIFAP has also been advocating with others for the wider provision of sexuality and life skills education in schools, work that was rewarded in 1998 when the Ministry of Education announced its support for comprehensive sexuality education in the standard school curriculum. IMIFAP's strategies for formulating, implementing and evaluating an integrated programme of sexuality education in a developing country, and advocating for its inclusion in national curricula, could serve as a model which others can adapt.