The activities of phenylalanine ammonia lyase and caffeate-0-methyl transferase in bean callus tissue, during differentiation, were induced in a coordinated manner over a period of 21 days. Neither enzyme activity could be induced to increase when differentiation was repressed by the addition of abscisic acid to the induction medium. The formation of soluble phenols was also increased during the induction of differentiation but it was also increased by the transfer to induction medium of an old callus which could no longer differentiate. PAL activity was more directly correlated with xylogenesis and nodule induction than with the formation of soluble phenols. Peroxidase activity in the callus tissue was always high but the level decreased during the induction of differentiation. A new isoenzyme of peroxidase was induced during callus formation and this was probably a response to the presence of auxins in the medium used to grow the callus.