Previous studies have identified low patient accrual in large-scale cancer clinical trials, particularly for underrepresented groups, such as ethnic minorities, females, and patients >65 years. As there have been few studies examining participation in cancer genetics epidemiologic research, our objective was to identify clinical and demographic factors predicting enrollment in these studies. A total of 1,111 patients diagnosed with colorectal cancer presenting to a gastrointestinal oncology clinic were approached to enroll in a study investigating the role of the MSH6 gene in familial colorectal cancer. Patient consent was sought for providing a blood specimen for DNA analysis and review of medical records/tumor specimens and contacting family members to confirm the family history of cancer. Seven predictor variables for enrollment (age, sex, ethnicity, family history of colorectal cancer in a first-degree relative, presence of children, insurance type, and type of visit) were analyzed using logistic regression analysis to determine the effect on decision to enroll. Of 1,111 patients approached, 696 (62.6%) enrolled in the study. Of these approached individuals, 4.2% were of nonwhite ethnicity and 33.5% were age > or =65 years. Patients of white ethnicity [odds ratio (OR), 2.10; P = 0.018], males (OR, 1.47; P = 0.002), those ages < or =65 years (OR, 1.42; P = 0.009), and those with a first-degree relative with colorectal cancer (OR, 1.57; P = 0.005) were significantly more likely to enroll. Fewer than 4% of all participants denied permission for the study researchers to access information from medical records or to be recontacted by researchers to discuss the enrollment of additional family members. Our data suggest that, once subjects decided to enroll, the majority (88%) was comfortable with consenting to all study components, including the creation of cell lines and future recontact. Low participation rates for ethnic minorities, females, and elderly patients are similar for both cancer genetics and clinical trial studies.