Algal polysaccharides such as carrageenan are good sources of dietary fibre. Previous studies have shown that carrageenan has hypoglycemic effects, but its cholesterol and lipid-lowering effects have yet to be demonstrated. In this study, carrageenan was incorporated into 4 food items, then fed to 20 human volunteers to determine its effects on blood cholesterol and lipid levels. The study followed a randomized crossover design. Each phase of the study--control and experimental--lasted for 8 weeks separated by a 2-week washout. At control, the subjects consumed their usual food intake; at experimental, they were given test foods with carrageenan partly substituting similar items in their usual diet. Fasting venous blood samples were collected immediately before and after each phase to assay serum cholesterol and triglyceride. The mean serum cholesterol was significantly lower (P<0.0014) after the experimental phase at 3.64 mmol/L compared with the mean level after the control phase, 5.44 mmol/L. The mean triglyceride level after the experimental phase, 0.87 mmol/L, was significantly lower (P<0.0006) in comparison to the level after the control phase, 1.28 mmol/L. The mean HDL cholesterol level significantly increased (P<0.0071) after the experimental phase at 1.65 mmol/L compared to the mean value after the control phase, 1.25 mmol/L. No significant differences were observed between the LDL cholesterol levels after the experimental and the control phases. This study indicates that regular inclusion of carrageenan in the diet may result in reduced blood cholesterol and lipid levels in human subjects.