Previous research has documented a need for the development of a sex education programme in Turkish schools in terms of adolescence readiness and the presence of misconceptions regarding critical aspects of sexual issues. Currently no school-based sex education is available for Turkish adolescents. This paper presents the development of a contemporary sex education programme for 12-year-old to 14-year-old adolescents, entitled "The Human Development Program for 12-14 Year Old Adolescents". A five-step programme development model was used including reviewing internationally recognised sex education programmes for this age group. Sexuality Information and Education Council of United States guidelines were chosen as an educational framework, and Turkish cultural values were integrated into the curriculum. The sex curriculum consists of an eight-session interactive programme in which parental permission and involvement is required. Five units are presented: human development, relationships, sexual behaviour, sexual health, and society/culture. The programme and a related knowledge assessment tool were reviewed by a group of Turkish professionals and the validity of the educational content was received. The programme was piloted with a group of Turkish adolescents with positive results. Future recommendations include school counsellors implementing this sex educational programme into Turkish schools. (Contains 1 table.)