Twelve normolipidic healthy human subjects were fed a diet with or without additional soybean phytosterols for 4 weeks in a crossover design. The order of the treatments was randomized. Phytosterols were added to the diet blended in butter. The dietary ratio cholesterol:phytosterols was 0.7 during the control period (436 mg cholesterol/day and 29 mg phytosterols/day) and 1.88 during the phytosterols period (410 mg cholesterol/day and 740 mg phytosterols/day). Blood cholesterol was 10% lower after subjects consumed the phytosterol-enriched diet than when they consumed the control diet (p < 0.001), which was due to a 15 % LDL cholesterol decrease (p < 0.001). The HDL cholesterol:LDL cholesterol ratio was markedly enhanced (+25%) (p < 0.01). These findings suggest that a significant lowering of plasma total and LDL cholesterol can be effected by a modest dietary intake of soybean phytosterols.