A 5-year trial involving 201 men and women with high-normal blood pressure at baseline demonstrated the ability to reduce the incidence of hypertension in participants randomized to nutritional-hygienic intervention compared with a control group. The incidence of hypertension was 8.8% among 102 intervention group participants vs 19.2% among 99 control group members. The odds ratio for the incidence of hypertension in the control group was 2.4. Mean trial blood pressure also was lower in the intervention compared with the control group (-1.2 and -1.9 mm Hg, respectively, for diastolic blood pressure at work-site and office visits and -1.3 and -2.0 mm Hg, respectively, for systolic blood pressure at the two sites). Net weight loss in the intervention group averaged 2.7 kg during the trial; sodium intake was reduced by 25% and reported alcohol intake decreased by 30%. The majority of intervention participants also reported an increase in physical activity. Effect on blood pressure was related particularly to degree of weight loss. Results indicate that even a moderate reduction in risk factors for hypertension among hypertension-prone individuals contributes to the primary prevention of the disease.