During May 1987, a total of 10,207 Wisconsin women were screened as part of a statewide Breast Cancer Detection and Awareness program sponsored by the Wisconsin Division of the American Cancer Society. Data from a population-based cancer reporting system were used to predict the number of expected breast cancer cases for that year. After controlling for secular and seasonal trends, we found that, compared with the number of cases that would have been expected, 51 more cases of localized breast cancer were diagnosed in the state during the time of the program. This study demonstrates the public health impact of a statewide screening program and the usefulness of a cancer reporting system in program evaluation.