Physical fitness is a powerful marker of cardiovascular health already at early stages in life. To promote physical fitness enhancement from the school is therefore needed. The present study describes a school intervention program specifically designed for these purposes, called EDUFIT (EDUcation for FITness). The study was carried out in 2007 and comprised 67 adolescents aged 13+/-1 years from a secondary school who belonged to three different classes. The classes were randomly allocated to control group (CG), experimental group 1 (EG1) and experimental group 2 (EG2). The CG was involved in 2 physical education sessions/week, the EG1 was involved in 4 physical education sessions/week (volume increased) and the EG2 was involved in 4 physical education sessions/week of high intensity (volume+intensity increased). Several health parameters were assessed before and after a 16-weeks intervention: physical fitness, body composition, lipid-metabolic profile, ventilatory parameters, blood pressure, and cognitive and academic performance. The intervention was feasible and well-tolerated. There were high participation and adherence rates, i.e. 96% (n=67) and 84% (n=56) respectively. Yet not always significant (0,1>P>0,05), we observed that the adolescents who satisfactory complete the program showed better cognitive and academic performance, and worse levels of adiposity, diastolic tension, handgrip strength and maximal expiratory pressure. The hypothesis of the EDUFIT study is that to double the number of physical education classes will improve physical fitness in adolescents. The confirmation of the hypothesis could have important public health implications.