AbstractJapanese lacquer is a sole, enzymatically drying natural lacquer, giving films with excellent durability. Oligomerization of urushiol (1) (a major component of the lacquer) in the lacquer system was reviewed. The enzymic formation of the urushiol‐quinone (3) from urushiol was studied by laccase‐catalyzed reactions with pyrocatechols. On the basis of the separated urushiol dimers in both the lacquer and model reaction systems, a nonenzymatic CC and CO coupling reaction of the urushiol‐quinone with the unsaturated chain or with the nucleus of urushiol is discussed as significant reaction path in the polymerization of Japanes lacquer. The films of the lacquer made by a mild oxidation process, a technique applied for so long time in practice, retained their dynamechanical properties completely over