We examined the relation between intake of natural dietary plant sterols and serum lipid concentrations in a free-living population. Cross-sectional population-based study of 22,256 men and women aged 39-79 y resident in Norfolk, UK, participating in the European Prospective Investigation into Cancer (EPIC-Norfolk). MAIN EXPOSURE AND OUTCOME MEASURES: Plant sterol intake from foods and concentrations of blood lipids. Mean concentrations of total cholesterol and low-density lipoprotein cholesterol, adjusted for age, body mass index and total energy intake, decreased with increasing plant sterol intake in men and women. Mean total serum cholesterol concentration for men in the highest fifth of plant sterol intake (mean intake 463 mg daily) was 0.25 mmol/l lower and for low-density lipoprotein cholesterol 0.14 mmol/l lower than those in the lowest fifth of plant sterol consumption (mean intake 178 mg daily); the corresponding figures in women were 0.15 and 0.13 mmol/l. After adjusting for saturated fat and fibre intakes, the results for total cholesterol and low-density lipoprotein cholesterol were similar, although the strength of the association was slightly reduced. In a free-living population, a high intake of plant sterols is inversely associated with lower concentrations of total and low-density lipoprotein serum cholesterol. The plant sterol content of foods may partly explain diet-related effects on serum cholesterol concentration.