An association of blood lipids with the development of atherothrombotic brain infarction under age 60 is demonstrated. This is based on 18 years' surveillance of 5,209 men and women, of whom 52 men and 59 women developed brain infarction. The relationship under age 60 was statistically significant only for men.Triglyceride-rich pre-beta and cholesterol-rich beta lipoprotein were both related to the incidence of premature brain infarctions. Regardless of associated lipoprotein pattern, risk was proportional to serum cholesterol value, under age 60. On the other hand, pre-beta lipoprotein was unrelated to risk when associated cholesterol was taken into account.At any lipid value risk of brain infarction varied greatly depending on the number and intensity of other contributors. Blood lipids are best considered as an ingredient of a stroke profile, and in the absence of other contributors to risk the influence of lipid is feeble.