A combination of the phytohormones naphthalene acetic acid and benzylaminopurine (5gM each) allows Lignification in various plant cell cultures. This system has been used to investigate the relationship between the coniferin-hydrolyzing 13-glucosidase activity and lignification. In Petroselinum hortense and Triticum aestivum cell cultures the appearance of this enzymatic activity coincided with lignification. In parsley cell cultures it was moreover shown that this activity appears concomitantly with other lignin biosynthetic enzymes. The unique enzymes of the flavonoid pathway did not appear by this phytohormone treatment. In other cell cultures investigated the correlation between the coniferin-hydrolyzing activity and lignification was not as evident as in the above two cases. This was probably due to the high activity of coniferin glucosidase already present in the normally grown cultures. Coniferin t3-glucosidase was found in all lignified cell cultures.