Recommendations for decreasing the risk of developing cardiovascular disease include increasing the intake of plant sterols and fish oil. The cholesterol-lowering action of plant sterols, when provided in a fish-oil fatty acids vehicle, remains to be investigated in humans. A randomized, crossover-feeding, single-blind trial was conducted in 30 subjects with mild-to-moderate hypercholesterolemia to study the effects on plasma lipids of 2 novel forms of plant sterols: those combined with, or esterified to, fish-oil fatty acids. The treatments were margarine (control), free plant sterols, plant sterols esterified to fatty acids from sunflower oil, plant sterols esterified to very long-chained fatty acids from fish oil, and plant sterols combined with the same amount of very long-chained fatty acids from fish oil. Each sterol-containing food (1.0-1.8 g plant sterols/d) was consumed for 29 d as a single dose with breakfast under staff supervision. Compared with the control treatment, none of the plant sterol preparations reduced plasma total cholesterol or LDL cholesterol, triacylglycerol, apolipoprotein A-I, apolipoprotein B, lipoprotein (a), or C-reactive protein concentration. Relative to the control phase, all plant sterols treatment increased the plasma HDL cholesterol concentration (P < 0.05) by approximately 8%. In conclusion, because standard forms of plant sterols did not reduce plasma cholesterol concentrations, the efficacy of the new formulation of plant sterols cannot be confirmed from the present study design, where plant sterols were given as a single morning dose.