This chapter deals exclusively with the chemistry of the odoriferous constituents of the volatile part of the flavor, namely the aroma. Three beverages, which are consumed in the form of suspensions or infusions, have in common that they come from stimulant plants originally growing in tropical regions. The three beverages are coffee, cocoa, and tea. The similarity between coffee and tea appears in the common content of 31% of the alcohols, 24% of the acids, 23% of the hydrocarbons and aldehydes, and 21% of the pyridines. The substituents of the furan ring can contain a wide variety of single or combined chemical functions: alcohols, aldehydes, ketones, acids, esters, mercaptans, and sulfides. It is evident that the originality of coffee flavor is mainly due to the fact that it contains 96% of the 26 thiophenes, 79% of the furans, 70% of the pyrroles, and nearly 60% of the oxazoles, thiazoles, and phenols.