Abstract Since both lignin and proanthocyanidins (including condensed tannins are frequently found together in woody plants, a common structural role has sometimes been postulated. These two phenolic polymers (or oligomers) are compared in terms of their stereochemistry, absorption spectra, biosynthetic pathways, intracellular and tissue localization, solubility, concentration and association with carbohydrates. The present evidence indicates that a common function in defense is more plausible than in structural support. The need for new histochemical techniques and the possibility of secondary changes in chemical composition and in localization of proanthocyanidins as cells die in normal development are discussed.