The effect of different phenolic compounds: p-hydroxybenzoic acid, resorcinol and chlorogenic acid (mono-, di-and polyphenol) was studied on nodulation and related metabolic processes in pigeonpea (Cajanus cajan L. cv. Al-15). Nitrogenease activity, leghaemoglobin and ascorbic acid content of the nodules increased with the application of phenols. Phenols increase the contents of amino acids, proteins and total soluble ~arbohydrates in the nodules as reserve food materials.