Within the context of an organized breast cancer screening program we conducted a prospective evaluation of the relation between breast cancer risk and participation in mammographic screening. The influence on participation of known breast cancer risk factors, as well as a summary risk label, (i.e. "high", or "moderate") were examined. The overall participation rate was 71 percent among 2,422 women, 50 to 79 years of age, invited to a centralized clinic. Multivariate analyses showed participation to be somewhat decreased among women with late menopause and definitely increased among women with any of the following factors: 1) increased age; 2) a family history of breast cancer; and 3) a previous breast biopsy. Women in the high-risk group were most likely to participate but the effect of the label was stronger among women ages 50 to 59 compared to women ages 60 to 79. The study results are generally consistent with previous findings that participants in screening programs have higher rates of breast cancer. The results also suggest the possibility that providing breast cancer risk information may encourage participation in screening.