This chapter has compiled and evaluated the current information on the methylxanthine composition of cocoa and various chocolate foods and beverages, as well as the consumption pattern for these commodities. Although the earliest recorded reference to cacao was in 1502, it was not until 1876 that milk chocolate was invented, an event that formed the backbone of the chocolate industry today. The consumption of cocoa throughout the world has been influenced by a number of factors, and the period of peak consumption occurred during the early to mid-1960s when these factors were highly favorable. The greatest consumption of cocoa in metric tons over the past 10 yr has been in the United States, although the highest per capita consumer during this period was Switzerland. The African continent has been historically the primary producer of raw cocoa, with the Ivory Coast currently being the largest individual supplier. Limited marketing survey data is available for the consumption of methylxanthines in chocolate foods and beverages. In children and teenagers, the major dietary source of caffeine was found to be tea, followed by soft drinks and coffee, respectively. Although chocolate foods and beverages ranked the lowest of these dietary sources to provide caffeine, they do constitute the major source of dietary theobromine. Cacao is the major natural source of the xanthine base theobromine. Small amounts of caffeine are present in the bean along with trace amounts of theophylline. The methylxanthine content of beans varies with the varietal type, and is influenced by the fermentation process. Chocolate liquor is a semifinished product commonly called "baking" or "cooking" chocolate. The average theobromine and caffeine content of liquors has been reported at 1.2% and 0.21%, respectively. Cocoa powder, which is prepared after removal of the cocoa butter, contains about 1.9% theobromine and 0.21% caffeine. Chocolate beverages comprise the most widely studied category of chocolate products. Hot cocoa provides 62 mg/serving of theobromine and 4 mg/serving of caffeine when prepared from commercial instant mixes. Instant cold chocolate milk mixes supply an average of 58 mg/serving of theobromine and 5 mg/serving of caffeine. The methylxanthine content of chocolate foods has received only slight attention in the literature. The methylxanthine content of sweet chocolate ranges from 0.359 to 0.628% for theobromine and 0.017 to 0.125% for caffeine.(ABSTRACT TRUNCATED AT 400 WORDS)