The effects of the soluble fiber konjac glucomannan (GM) on serum cholesterol concentrations were investigated in 63 healthy men in a double-blind crossover, placebo-controlled study. After a 2-wk baseline period, the subjects were given 3.9 g GM or placebo daily for 4 wk. After a washout period of 2 wk, crossover took place, followed by another 4 wk of treatment. The subjects were encouraged not to change their ordinary diets or general lifestyle during the investigation. GM fibers reduced total cholesterol (TC) concentrations by 10% (P < 0.0001), low-density-lipoprotein cholesterol (LDL-C) concentrations by 7.2% (P < 0.007), triglycerides by 23% (P < 0.03), and systolic blood pressure by 2.5% (P < 0.02). High-density-lipoprotein cholesterol (HDL-C) and the ratio of LDL-C to HDL-C did not change significantly. No change in diastolic blood pressure or body weight was observed. No adverse effects were observed. The results of this study show that GM is an effective cholesterol-lowering dietary adjunct.