The storage modulus (E＇) and loss modulus (E ") of Japanese lacquer films were measured over a temperature range of -150 to 400 degrees C. Three relaxation processes labeled alpha, beta, and gamma were detected at 80, -60, and - 140 degrees C, and their apparent activation energies (Delta E) were 63-91, 13, and 9 kcal/mol, respectively. These were attributed to the micro-Brownian motions of polymerized urushiol, the molecular motion related to the absorbed water, and the motions of methylene soups in the side chains, respectively. With aging at room temperature, the location of the oc peak shifted to higher temperature and its Delta E value decreased. This result was ascribed to the autoxidative polymerization of urushiol. The E＇ of lacquer films increased with heat treatments at 100 degrees C or above. When treated at temperatures below 200 degrees C, the location of the alpha peak shifted to higher temperature, with a reduction in the Delta E value. Heat treatments at 200 degrees C or above resulted in remarkable shrinkage and weight loss of films owing to the pyrolysis of lacquer constituents.