Summary Acyltransferases which catalyze the formation of hydroxycinnamic acid esters of sugar acids (gluconate, glucarate, galactarate, glucarolactone) and hydroaromatic acids (quinate, shikimate) involving hydroxycinnamoyl-CoAs as acyl donors have been partially purified from primary leaves of rye (Secale cereale L.). The enzymes were retained on a diethylaminoethylcellulose column and were eluted as distinct, acceptor-specific activities. Some properties of the enzymes are described. The development of the enzyme activities during leaf growth correlated with the accumulation patterns of the in vivo major products, p-coumaroylglucarate, feruloylglucarate, feruloylgalactarate, feruloylglucarolactone, and sinapoylglucarolactone. The esters accumulate transiently to large amounts, indicating metabolic activity. During decrease of the concentrations of soluble esters corresponding amounts of p-coumaric and ferulic acids were found to accumulate as insoluble esters, most likely bound to cell wall material.