Detailed examination of the reaction of quinoline 1-oxide (1) with methacrylonitrile in the presence of acetic anhydride and the re-examination of the reaction of 1 with acetic anhydride have revealed that there is another reaction sequence leading to polyquinolylmethanes, [tri-(2-quinolyl) methane (5), N-(2-quinolyl)-2-(2-quinolylmethylene)-1, 2-dihydroquinoline (11) and N-(2-quinolyl)-2-[di-(2-quinolyl) methylene]-1, 2-dihydroquinoline (6)], besides the formation of carbostyril in the latter reaction. Reactions of 1 with acetic anhydride in the presence of quinaldine, di-(2-quinolyl)-methane (9), cyanoacetic acid, malonic acid and phenylacetic acid were also examined in connection with the exploration of the mechanism of the above reaction, and the possible mechanism has been proposed.