Tasting of pure compounds and various fractions isolated from black tea liquors suggests that, with the exception of caffeine, none of the characteristic monomeric nonvolatile substances contributes significantly to the taste of the beverage. The most important of the nonvolatiles are complex products formed by oxidation and polymerization of polyphenols during processing of the leaf. The molecular weight distribution of these products, their degree of association with protein, and their interaction with caffeine are of major importance in determining the ‘mouthfeel’ characteristics of tea. © 1969, American Chemical Society. All rights reserved.