Introduction: Sex-specific differences in observed incidence rates, tumor subsite, and diet and lifestyle associations with colon cancer have been observed. We evaluate sex-specific associations with p53 mutations in colon cancer to add to understanding of these differences. Data from a large population-based incident case-control study of colon cancer were used to evaluate age and gender associations with p53 mutations. To obtain a better understanding of gender-specific associations, we evaluated the role of estrogen as a mediator of risk. For these analyses, women were classified as estrogen positive or negative, based on menopausal status and use of hormone replacement therapy (HRT). Results: There was a significant interaction between age and sex and risk of an acquired p53 mutation compared with p53 Wt. Among men, there was an increase in p53 mutations with age, whereas among women the opposite was observed. Associations with parity, oral contraceptive use, and total ovulatory months were not associated with p53 mutations. However, recent use of HRT reduced risk of all tumors, as did being estrogen positive. Women who were estrogen positive (either premenopausal or recent users of HRT) were at a significantly increased risk of an acquired p53 mutation if they consumed a diet with a high sugar index (odds ratio = 2.94; 95% confidence interval = 1.47-5.89); similar increases in risk of p53 mutations were not observed for menor or women who were estrogen negative. Conclusions: Although sex-specific associations were detected for acquired p53 mutations, they do not indicate a unique role of estrogens in the mutation of p53. These data are consistent with a role for estrogen in altering susceptibility to diet and lifestyle factors possibly via an insulin-related mechanism.