Guidelines for the use of water-soluble dietary fibers (WSDF) in the dietary management of elevated plasma cholesterol are not well-established. Consequently, 4 studies were conducted to explore the plasma lipid-lowering effects of a variety of WSDF. Studies were randomized, double-blind, placebo-controlled trials involving healthy men and women (plasma cholesterol greater than 5.17 mmol/liter; greater than 200 mg/dl). Study duration ranged from 4 to 12 weeks. The WSDF acacia gum yields a low viscosity, palatable beverage when mixed in water. However, despite its WSDF classification, acacia gum consumed for 4 weeks as the sole WSDF source (15 g of WSDF/day) or primary source in a WSDF mixture (17.2 g of WSDF/day; 56% derived from acacia gum) did not produce a significant lipid-lowering effect versus placebo. When 15 g of WSDF/day consisting of psyllium hust, pectin, and guar and locust bean gums (medium viscosity) was consumed for 4 weeks, significant reductions in cholesterol resulted (total cholesterol 8.3%, low-density lipoprotein cholesterol 12.4%; p less than 0.001) that were comparable to changes achieved with 10 g of WSDF/day from high-viscosity guar gum. The magnitude of the lipid-lowering effect was related to intake of WSDF ranging from 5 to 15 g/day (low-density lipoprotein cholesterol +0.8% [placebo], -5.6% [5 g/day], -6.8% [10 g/day], -14.9% [15 g/day]; p less than 0.01 for trend). The effects of WSDF on plasma lipids were similar for men and women. A diet rich in selected WSDF may be a useful adjunct to the dietary management of elevated plasma cholesterol.