Eighteen normolipidemic males were fed six different species of shellfish; each shellfish was fed so that protein in shellfish equalled that in animal foods in the normal diet, with less than one-half of the amount of fat in animal foods allowed for preparation of the shellfish. Oyster, clam, crab, and mussel diets, low in cholesterol and high in n-3 fatty acids, lowered VLDL triglycerides and cholesterol and, except for the mussel diet, LDL and total cholesterol. Squid and shrimp diets, higher in cholesterol and lower in n-3 fatty acids, did not change the blood lipids. The ratio of LDL to HDL cholesterol was decreased on the oyster and mussel diets. Oyster, mussel, and squid diets increased HDL2 cholesterol. Cholesterol absorption was decreased on the oyster, clam, and mussel diets. When consumed with moderate dietary fat restriction, oysters, clams, mussels, and crab appear to be useful in hypolipidemic diets for normolipidemic men.