This paper has two objectives that are addressed from a developmental contextual perspective which relates developmental transitions, developmental tasks and skills in adolescence. First, a study is presented in which adolescents' reports on their contextual and personal functioning, obtained from a sample of 1433 adolescents aged 13 to 17 years, were related to their lifestyle. In particular, we sought to examine how lifestyle patterns were related to adolescents' functioning in peer, school and neighbourhood contexts, as well as to their personal characteristics such as internal locus of control, personal achievement and behavioural problems associated with self-regulation. The results revealed aclose correspondence between contextual adjustment, personal characteristics and health-related patterns. Second, a prevention program, "Construyendo mi futuro" (Building my future), aimed at supporting vulnerable adolescents through their developmental transitions is described. According to the above framework the program promotes the learning of individual, interpersonal and group skills in the actual life contexts where the adolescents' development takes place. A detailed description of the program's aims, characteristics, content, methodology and evaluation design is provided. Finally, preliminary results regarding the program's efficacy are also presented.