Three lacquer samples taken from a "four-eared" pottery container, which was designated an important National Cultural Property of Japan excavated in 16-17th century ruins of Kyoto City, were analyzed by pyrolysis-gas chromatography! mass spectrometry (Py-GC/MS) and infrared (IR) spectroscopy to determine the source of the lacquer. It is an unexpected result that the lacquer in this pottery container is actually used by Melanorrhoea usitata. Alkylbenzene and alkenylbenzene as cleavage pieces of undecylbenzene (MW = 232 g/mol) and undecenylbenzene (MW = 230 g/mol), which are products of the pyrolysis of thitsiol, were detected in all three samples. Moreover, omega-phenylalkylcatechols and omega-phenylalkylphenols, which are the specific components of M. usitata, were also detected by Py-GC/MS, suggesting that lacquer sap of M. usitata was used by the Japanese people in the 16-17th centuries. In addition, Japanese lacquer culture and the advantages of the Py-GC/MS method for lacquer analysis are discussed in detail. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 897-901, 2010