The mutagenic compound 2-amino-3-methylimidazo[4, 5-f]quinoline, originally isolated from broiled sardines and also present in cooked beef and beef extract, is being tested for carcinogenicity in F344 rats of both sexes. High incidences of tumors of the Zymbal gland, colon, small intestine and liver in males have been observed in the first 300 days of the experiment.