The evidence is growing that not only total cholesterol, but also HDL cholesterol is an important predictor of coronary heart disease. In the Framingham Study, the total cholesterol/HDL cholesterol ratio gave the best prediction for the coronary heart disease risk. With data of the Netherlands Monitoring Risk Factor Project it was investigated to what extent persons with a high ratio (greater than or equal to 7) were identified when the criteria of the Netherlands Cholesterol Consensus were applied. Between 1987 and 1989 total and HDL cholesterol were determined in about 22,000 men and women aged 20-59. Twenty per cent of the men had hypercholesterolaemia (total cholesterol greater than or equal to 6.5 mmol/l). Of the hypercholesterolaemic men, 60 per cent did not have a high total/HDL cholesterol ratio. Eighteen per cent of the women were hypercholesterolaemic. Of all hypercholesterolaemic women, 80 per cent did not have a high total/HDL cholesterol ratio. Therefore, it is important that after a first screening on total cholesterol, HDL cholesterol is measured at the second cholesterol determination. Subsequently, a decision about treatment should be made, based on the total/HDL cholesterol ratio and the presence of other risk factors (hypertension, smoking, obesity, diabetes and a family history of cardiovascular disease.