While there is no convincing direct evidence of an influence of specific dietary factors on breast cancer in women, the overall geographic correlation between risk of breast cancer and food consumption patterns suggests a positive link. Epidemiologic studies have correlated breast cancer rates with fat consumption. Increased dietary fat, through intestinal microflora production of estrogens, might expose breast tissue to chronic, excessive stimulation and increase cancer risk. Laboratory animal studies have shown that dietary fat affects response to DMBA carcinogenesis. Studies in our own laboratory have shown that 20% corn oil or lard increased DMBA mammary tumorigenesis, compared to rats fed 5% fat; 20% corn oil accelerated sexual maturation, but 20% lard did not. The mechanisms of tumorigenesis under such circumstances are unknown.