Sitosterol has previously been shown to block cholesterol absorption in both animals and man. Its clinical effectiveness in reducing hypercholesteremia has been repeatedly demonstrated. For periods exceeding 4 years, large amounts of sitosterol have been given daily for maintaining reduction of serum cholesterol concentration. The possibility of adverse side effects resulting from chronic administration has been considered. Long-term animal and clinical studies indicate that sitosterol has no detectable toxicity and does not accumulate or deposit in tissues.