The effects on blood lipids and blood pressure of a diet corresponding to present Nordic Nutrition Recommendations, i.e. less than 30% of energy from fat and with a fibre content exceeding 3 g/MJ, were studied in 18 men and 12 women (mean age, 24 years) under strict dietary control over 8 months. Blood sampling, blood pressure and body weight measurement were performed at four occasions on their habitual diet and once a month during the intervention period. An age-matched control group (17 men, 8 women) was followed with monthly measurements parallel to the intervention group. The habitual diets, assessed by 7-day records, showed an average fat content corresponding to 36% of energy. Initial levels of total cholesterol and HDL cholesterol (X +/- SD) were 4.21 +/- 0.61 and 1.23 +/- 0.23 mmol/l for the men in the intervention group; 4.35 +/- 0.79 and 1.21 +/- 0.26 mmol/l for the male controls; 4.61 +/- 0.59 and 1.46 +/- 0.31 mmol/l for the women in the intervention group and 4.48 +/- 0.64 and 1.48 +/- 0.29 mmol/l for the female controls. Significantly decreased levels of total cholesterol and HDL cholesterol throughout the experimental period were seen for both sexes in the intervention group. Total cholesterol fell 0.49 mmol/l (95% CI: 0.41-0.56) in the male subjects and 0.49 mmol/l (95% CI: 0.39-0.59) in the female subjects. The fall in HDL cholesterol was 0.16 mmol/l (95% C: 0.13-0.18) and 0.18 mmol/l (95% CI: 0.12-0.23), respectively. Total cholesterol changes were independent of initial values. All subjects were normotensive at the start of the study with an average blood pressure of 122/68 mmHg for men and 112/68 mmHg for the women. Systolic blood pressure dropped gradually and significantly in the male subjects of the intervention group. A minimum of 6 mmHg below initial values was noted after six months of dietary intervention. No significant changes in dietary intake and blood lipids were observed in the control group. Thus, changes of present dietary habits of young healthy Danish subjects to an intake in accordance with the Nordic Nutrition Recommendations 1989 will favourably affect suggested risk factors for disease.