Background: Phytosterol supplementation of 2 g/d is recommended by the National Cholesterol Education Program to reduce LDL cholesterol. However, the effects of different intakes of phytosterol on cholesterol metabolism are uncertain. Objective: We evaluated the effects of 3 phytosterol intakes on whole-body cholesterol metabolism. Design: In this placebo-controlled, crossover feeding trial, 18 adults received a phytosterol-deficient diet (50 mg phytosterols/2000 kcal) plus beverages supplemented with 0, 400, or 2000 mg phytosterols/d for 4 wk each, in random order. All meals were prepared in a metabolic kitchen; breakfast and dinner on weekdays were eaten on site. Primary outcomes were fecal cholesterol excretion and intestinal cholesterol absorption measured with stable-isotope tracers and serum lipoprotein concentrations. Results: Phytosterol intakes (diet plus supplements) averaged 59, 459, and 2059 mg/d during the 3 diet periods. Relative to the 59-mg diet, the 459- and 2059-mg phytosterol intakes significantly (P < 0.01) increased total fecal cholesterol excretion (36 ± 6% and 74 ± 10%, respectively) and biliary cholesterol excretion (38 ± 7% and 77 ± 12%, respectively) and reduced percentage intestinal cholesterol absorption (-10 ± 1% and -25 ± 3%, respectively). Serum LDL cholesterol declined significantly only with the highest phytosterol dose (-8.9 ± 2.3%); a trend was observed with the 459-mg/d dose (-5.0 ± 2.1%; P = 0.077). Conclusions: Dietary phytosterols in moderate and high doses favorably alter whole-body cholesterol metabolism in a dosedependent manner. A moderate phytosterol intake (459 mg/d) can be obtained in a healthy diet without supplementation. This trial was registered at clinicaltrials.gov as NCT00860054.