The National Cholesterol Education Program (NCEP) guidelines recommend dietary restriction of fat and cholesterol to reduce high circulating cholesterol concentrations in adult Americans. Thus, diet counselors recommend consumption of fewer than four egg yolks per week. The present protocol was designed to determine whether the efficacy of an NCEP diet would be reduced by the incorporation of 12 modified eggs per week, and whether the resulting low fat, high cholesterol diet would increase serum lipid concentrations in adults with initial undesirably high (5.17-7.76 mmol/L) concentrations of serum total cholesterol. Feeding a controlled ration to laying hens produced modified eggs that consistently contained more vitamin E and iodine, and more unsaturated fat, than generic eggs. Subjects were randomly assigned to and NCEP diet including either no whole eggs or 12 whole study eggs a week. Ninety-eight subjects completed the parallel study. Subjects in both groups significantly reduced their serum total, LDL and HDL cholesterol (P < 0.001 for total and LDL cholesterol, P < 0.02 for HDL cholesterol) over the 6 wk of study. No significant differences were found between diet groups. We conclude that the study eggs did not adversely affect measured lipid concentrations when added to a low fat diet that favorably alters lipid profiles in hypercholesterolemic subjects.