The mutagenicity of pyrolyzates (at 30$0^{circ}C$, $600^{circ}C$ and 75$0^{circ}C$) prepared from three kinds of Maillard reaction Products, KG-19, KG-24 and KG-32, and that of the tar of cigarettes added these products were determined by using Salmonella typhimurium TA 98. The pyrolyzates of Maillard reaction products showed linear increases of revertant colonies according to the increase of pyrolysis temperature and dose of pyrolyzates, respectively. However, there was no difference in revertant colonies between the tar of cigarettes containing these products and those containing imported Maillard reaction products, or not containing any reaction product. It seems due to a little amount of these products added to the cigarettes.