We have studied the determinants of total and high density lipoprotein (HDL) cholesterol in young boys from five countries characterized by different lifestyles, dietary consumption profiles and mortality rates from coronary heart disease. All measurements including the estimation of dietary intake, physical activity, body mass index and the concentrations of total and HDL cholesterol were carefully standardized. The mean concentrations of total and HDL cholesterol were higher in the European boys (4.1-4.9 mmol/l and 1.45-1.57 mmol/l, respectively) than in the boys from Ghana and the Philippines (3.3-3.8 mmol/l and 0.93-1.10 mmol/l, respectively). A positive correlation was found between the concentration of total cholesterol and the intake of saturated fatty acids in four out of five countries. The concentration of HDL cholesterol was also related to various dietary variables in some of the groups. Using the regression coefficients from a multiple regression analysis on the pooled data, it could be calculated that on average 24 per cent of the inter-country differences in the levels of total cholesterol is explained by differences in the intakes of saturated fatty acids. Differences between the groups of the different countries in the intakes of carbohydrate explained on average 29 per cent of the differences in the concentrations of HDL cholesterol. The results obtained support the hypothesis that higher concentrations of total and HDL cholesterol are associated with western types of diets rich in saturated fatty acids and relatively poor in complex carbohydrates.