4-Azidoquinoline 1-oxides with methyl, cyano and carbamoyl groups at the 2 position, and chloro and trifluoromethyl groups at the 7 position were prepared. 4-Azidocinnoline 1-oxide and 2-oxide were also prepared. Their antitumor and mutagenic activities were tested in comparison with those of a carcinogenic, carcinostatic and mutagenic compound, 4-nitroquinoline 1-oxide.