Technical Abstract: Shellfish commonly consumed in the U.S. were sampled and analyzed to update nutrient data in the United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference (SR), using a nationwide sampling plan and validated analytical methodology. In 2007-8, raw shrimp and sea scallops, steamed oysters, blue crab, lobster, and canned clams were sampled from 12 statistically selected supermarkets across the U.S. For each species, four composites each comprised of samples from 3 locations were analyzed; shrimp and scallops from 6 single locations were also analyzed. Fourteen sterols were determined in total lipid extracts after saponification and derivatization to trimethylsilyethers, using gas chromatography for quantitation and mass spectrometry for confirmation of peak identities. Crab, lobster, and shrimp contained significant cholesterol (96.2-127 mg/100g); scallops and canned clams had the lowest concentrations (23.4-30.1). Variability in cholesterol among single-location samples of shrimp was low. The major sterols in the mollusks were brassicasterol (12.6-45.6 mg/100g) and 24-methylenecholesterol (16.7-41.9), with the highest concentrations in oysters. Total non-cholesterol sterols were 46.5-75.6 mg/100g in five single-location scallops samples, but 107 in the sixth, with cholesterol also higher in that sample. Other prominent non-cholesterol sterols in mollusks were 22-dehydrocholesterol, isofucosterol, clionasterol, campesterol, and 24-norcholesta-5,22-diene-3ß-ol (4--21 mg/100g).