Effects of auxin and kinetin on growth and production of phenolic compounds in cultured Cassia fistula L. tissues were examined. Initiation of polyphenols was largely determined by the auxin concentration in the medium. Growth of the cells in relation to accumulation of polyphenols was studied at different auxin and kinetin concentrations. The accumulation of phenolic materials was essentially restricted to the most rapid phase of the growth cycle. Progressive changes in the pattern of peroxidase activity were followed and their relationship with polyphenol synthesis is examined.