Of an estimated pool of 1,700 potential participants, only 382 (22%) eligible women participated in a low-cost breast cancer screening program offered to university and medical center employees. Because most women were still available and data were needed to understand why the opportunity to participate was refused by so many, a survey was done to determine factors related to mammography behavior. Three distinct groups of women were identified according to health beliefs, mammography behaviors, and modifying factors. Women who participated in the mammogram program were predominantly well-educated working women who were aware of mammography and its relationship to the breast cancer trajectory; they were affected by cost and convenience issues. One group of women did not participate in the program offered because they had had a recent mammogram; these women were at high risk for breast cancer and perceived mammography to be beneficial. The women who did not participate for other reasons were in nonprofessional jobs, had lower levels of education, and tended not to participate in the health care system as readily as women in the other groups; they perceived themselves less susceptible to breast cancer, valued mammography less, and knew less about breast cancer.