The carcinogenicity of the mutagenic compound 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ), identified in fried and broiled foods, was investigated in female Sprague-Dawley rats. Administration by gavage of IQ (0.4 mmol/kg body weight) on a weekly regimen for 31 weeks starting with 6-week-old animals induced a high yield of multiple mammary gland carcinomas in a limited bioassay lasting a total of 52 weeks. In a positive control group receiving 4-aminobiphenyl (4-AB), the expected carcinomas in the mammary gland developed. IQ, but not 4-AB, also yielded neoplasms in the ear duct and to a lesser degree, in the liver, pancreas, and urinary bladder. In addition, with IQ, a high incidence of preneoplastic lesions in the pancreas was observed. Vehicle and untreated controls did not have any lesions. These findings demonstrate that IQ is a powerful multipotent carcinogen in the rat.