Background. An educational intervention program for the prevention of cardiovascular disease among 171 Cretan school students (13- and 14-year-olds) is assessed. Three schools from the province of Agios Vassilios acted as the intervention group while two schools from a neighboring province (Amari) formed the control group. Methods. Variables measured included: systolic and diastolic blood pressures, body mass index, triceps skinfold thickness, serum total and high-density lipoprotein cholesterol, triglycerides, and smoking habits. The intervention, based upon social learning theory, consisted of 10 sessions of theoretical and practical instruction on health issues in the classroom, supplemented with discussion, in the classroom, of the issues raised by different sessions. Results. At the end of 1 academic year of intervention the results showed, after adjusting for age, sex, baseline value, height, and weight, an increase in total serum cholesterol of 0.70 mg/dl in the intervention group and 17.91 mg/dl in the control group (P < 0.0001). Diastolic blood pressure (fourth phase) decreased by 2.95 mm Hg in the intervention group and by 0.48 mm Hg in the control group (P < 0.05). Similar changes were observed in the body mass index (P < 0.05). The proportion of school children starting smoking was significantly lower in the intervention group (6%) than in the control (20%) (P < 0.01). The results indicate that this health education program in schools is effective in decreasing some of the major CVD risk factors. The long-term effect remains to be evaluated.