Dietary resveratrol (3,4',5-trihydroxystilbene) has been implicated in the health benefits associated with grapes and red wine, more specifically with potential benefits for metabolic syndrome, energy use, and increased endurance. Levels of trans-resveratrol and its glucoside, trans-piceid, were determined in 19 top selling commercially available cocoa-containing and chocolate products from the U.S. market. Amounts of trans-resveratrol and trans-piceid were closely correlated with the amount of nonfat cocoa solids (NFCS) in the cocoa-containing products. Among these products, trans-resveratrol levels were highest in cocoa powders (1.85 +/- 0.43 microg/g), followed by unsweetened baking chocolates (1.24 +/- 0.22), semisweet chocolate baking chips (0.52 +/- 0.14), dark chocolates (0.35 +/- 0.08), milk chocolates (0.10 +/- 0.05), and chocolate syrups (0.09 +/- 0.02). These cocoa-containing and chocolate products have about 3-5 times more trans-piceid than trans-resveratrol. Levels of trans-piceid were highest in the cocoa powders (7.14 +/- 0.80 microg/g), followed by unsweetened baking chocolates (4.04 +/- 0.14), semisweet chocolate baking chips (2.01 +/- 0.18), dark chocolates (1.82 +/- 0.36), milk chocolates (0.44 +/- 0.06), and chocolate syrups (0.35 +/- 0.06). On an equal weight basis, cocoa powder had about half as much trans-resveratrol as the average California red wine. On a per serving basis, cocoa-containing and chocolate products had less trans-resveratrol than red wine and grape juice but more than roasted peanuts. Overall, these cocoa-containing and chocolate products rank second after red wines and grape juice in foods with the highest levels of total trans-resveratrol in the diet.