A descriptive genetic analysis (offspring between parent plot) was applied to serum cholesterol and triglyceride levels of 1044 Finnish subjects who were parents, siblings, spouses, and offspring of 204 male probands with angina pectoris or nonfatal myocardial infarction before age 55 years. The same analysis was also applied to 511 relatives of 106 control men matched to the probands for age and location (northeastern Finland or southern Finland). Striking differences in the plot results for triglyceride data suggest that male probands with angina pectoris as first evidence of coronary disease had different familial characteristics than those with nonfatal myocardial infarction at the onset. Further plot contrasts suggest stronger major gene effects for cholesterol and triglyceride levels in northeastern Finland, both in case and control families. Genetic makeup may help explain why men in northeastern Finland have the world's highest rate of early coronary heart disease.