A tryptamine-forming, L-tryptophan decarboxylase (E.C. 4.1.1.27) from tomato shoots, has been partially purified and characterized. The properties of the enzyme were compared with those of tryptophan transaminase isolated from the same tissue, and separation of these two enzymes by ammonium sulphate fractionation clearly demonstrated that tryptamine formation was due to the activity of the decarboxylase enzyme. Tryptophan decarboxylase was found to be pyridoxal phosphate dependent and appeared to have substrate affinities different from those of 5-hydroxytryptophan decarboxylase (E.C. 4.1.1.28) found in animal tissue. The importance of tryptophan decarboxylase in the biosynthesis of indol-3yl-acetic acid is discussed.