In 2388 schoolchildren aged 9-12 years who took part in a study of cardiovascular risk factors in Westland, Holland, plasma sugar concentrations were found to be positively correlated with systolic and diastolic blood pressure, independently of weight. Serum cholesterol levels were also related to systolic blood pressure in boys, but much less strongly than plasma sugar levels. The relation between serum insulin and blood pressure, independent of plasma sugar, was weak. The relation between plasma sugar and systolic pressure existed for both sexes and regardless of whether measurements were made in the morning or afternoon; its association with diastolic pressure was weaker, and was not so consistent over all groups. These findings suggest that the relations between risk factors for coronary heart disease that exist in adults are already evident in childhood.