The purposes of this study were (a) to estimate the annual prevalence of, and to identify the predictors of, sexual infidelity in a population-based sample of married women (N = 4,884); and (b) to evaluate whether the prevalence and predictors of infidelity varied as a function of whether the assessment of infidelity was based on a face-to-face interview versus a computer-assisted self-interview. Annual prevalence of infidelity was much smaller on the basis of the face-to-face interview (1.08%) than on the computer-assisted self-interview (6.13%). Although many of the predictor variables replicated results from previous studies (e.g., demographic variables, religiosity, sexual experience), findings also indicated that childhood sexual abuse (i.e., forced sex) predicted greater probability of infidelity. Finally, the magnitude of the association with infidelity for 4 of the 9 predictor variables differed between the 2 methods for assessing infidelity. This study's findings underscore the importance of assessing infidelity with methods such as computer-assisted self-interviews that minimize the influence of social desirability and impression management.