The objectives of this research were to document adherence to mammography screening guidelines among women over 50 years of age and to investigate factors related to adherence. Selected sociodemographic variables--personal breast health history, provider-related variables, and medical care utilization--were studied. Data were collected through a random digit dial telephone survey of 693 women from two geographic areas. While 48% had had a mammogram in the last year, only 20% reported at least two recent mammograms at yearly intervals. Adherence was significantly associated with having a higher income, being white, being 51 to 64 years old and having had breast symptoms and/or a family history of breast cancer. Additionally, women who had a regular physician, higher frequency of clinical breast examination, and a recent physician visit were more adherent. Women enrolled in Health Maintenance Organizations (HMOs) and/or covered by commercial plans were more adherent than women with no insurance or with entitlement coverage only. These relationships were generally maintained in multivariate analysis. While this study is consistent with others that demonstrate increasing adoption of mammographic screening, it also illustrates that the goal of regular screening according to guidelines has yet to be achieved.