The relationship between hyperlipidemia and a parental history of heart attack and other related disorders was studied in 2224 two- to 18-yr-old children in Madrid (Spain). Children were divided into three groups: those with a parental history of heart attack (first group), a parental history of stroke, hypertension, diabetes mellitus or hypercholesterolemia (second group), and no parental history of disease (third group). The number of children with higher than normal levels of total cholesterol (greater than 200 mg/dl), LDL-cholesterol (greater than 135 mg/dl) and/or apolipoprotein B100 (greater than 75 mg/dl) was significantly higher in the first and second group (positive parental history) than in the third (no parental history). Children and adolescents with a parental history of heart attack (first group) had significantly higher mean levels of total cholesterol and LDL-cholesterol; in the 2- to 13-yr age group a significantly higher level of apolipoprotein B was also found. Children and adolescents belonging to the second group had a significantly higher level of LDL-cholesterol, and a significantly higher level of apolipoprotein B was also found in the 2- to 13-yr age group. However, only 15% of children with hypercholesterolemia had a parental history of heart attack or other related disorders. This percentage was 41% when second-degree relatives were included in the family history. We conclude that a parental history is not enough to detect children with an abnormal lipid profile who might be at risk for early development of coronary arterial disease.