Attitudes about genetic testing are likely to be an important determinant of uptake of predictive genetic tests among the general public. Several prior studies have suggested that positive attitudes about genetic testing may be inversely related to knowledge about genetic testing. We conducted a random-digit-dialing (RDD) telephone survey of 961 adults in the continental United States to determine the associations among knowledge of, attitudes about, and perceptions of eligibility for genetic testing for cancer risk. Knowledge about genetic testing for cancer risk was generally high, with a mean accuracy score of 72%. Attitudes about genetic testing for cancer risk were also generally positive, with 87% of respondents reporting genetic testing for cancer risk would be used to help doctors manage their health care and 85% to help scientists find cures for diseases. In contrast, 58% of respondents thought genetic testing for cancer risk would be used to prevent them from getting health insurance and 31% to allow the government to label groups as inferior. Twenty-nine percent of respondents thought they were currently eligible for testing. After adjustment for sociodemographic characteristics and family cancer history, higher knowledge was correlated with more positive attitudes about testing, but not with negative attitudes or perceptions of testing eligibility. Family history was positively associated with perceptions of eligibility (OR 3.49, 95%CI 2.36–5.18), and higher levels of education were inversely associated with perceptions of eligibility (OR 0.55, 95%CI 0.32–0.94 for comparison of college or higher vs. less than high school). These results suggest that most members of the general public are knowledgeable and have positive attitudes about genetic testing for cancer risk and that greater knowledge is correlated with more positive attitudes about the benefits of testing.