Fifty-one healthy, moderately hypercholesterolemic men and women consuming their usual fat-modified diets completed a 6-month, randomized, double-blind, placebo-controlled, parallel comparison of 15 g/day supplemental water-soluble dietary fiber (WSDF; a mixture of psyllium, pectin, guar gum, and locust bean gum) and an inactive WSDF control (acacia gum). Compliance with the treatments was>> 95%, adverse effects were minimal, and body weights remained constant. The WSDF mixture yielded 6.4% and 10.5% reductions in mean plasma total and low-density lipoprotein cholesterol concentrations, respectively, after 8 weeks, which were sustained at 16 and 24 weeks. Mean plasma high-density lipoprotein cholesterol and triglyceride concentrations were unchanged. No significant changes in mean plasma lipid or lipoprotein concentrations were observed in the control group. These data demonstrate that a WSDF approach to cholesterol management is effective as an adjunct to a fat-modified diet in healthy, moderately hypercholesterolemic men and women.