Enzymes for the biosyntheses of the major phenylpropanoid derivatives in vascular plants, namely flavonoids, lignins and cinnamyl esters are now known. The cinnamate pathway to these compounds is reviewed briefly and brought up-to-date. Remaining problems, such as the regulation by light and other factors as well as compartmentalization of phenylpropanoid metabolism are being studied in many laboratories. The physiological importance of low molecular weight cinnamyl compounds needs attention.Pioneer tracer studies by the schools of NEISH [24], FREUDENBERG [24] and This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.