Abstract: The effect of 15stilbenolus on protein kinase C(PKC)was studied in order tosearch for naturally occurring PKC inhibitors.All these compounds were isolated from Chinesemedicines. Three oligomeric stilbenes from Caragana sinica,α-viniferin ,kobophenol A and miyabenolC,were shown to intensely inhibit the activity of patially purified rat brain PKC with IC₅₀ values of62.5 ,52.0 ,and 27.5 μmol.L^-1 ,respectivel Kinetic analyses revealed that the inhibition wasnoncompetitive. The other compounds also showed the effect.Monomer stilbenes exhibited PKCinhibitory activity at higher μmol·L^-1 concentrations than oligomeric stilbenes.Whenever they aremethylated or acetylated perfectly , the inhibition weekens or disappears.