Data based on the 1987 National Health Interview Survey are presented depicting factors associated with the knowledge and use of three tests for the early detection of colorectal and prostate cancer: digital rectal examination, fecal occult blood tests, and flexible sigmoidoscopy. The percentage of the at risk adult population who have ever heard of or had these tests is reported. The association of demographic, personal resource, and health system factors with knowledge of these tests is explored using multivariate logistic regression. Health system factors are most consistently associated with use of the tests and with knowledge. Family income, family size, education, knowledge of cancer early warning signs, and measures of encounters with the health care system are associated both with knowledge of and, independent of knowledge, with use of the tests. Residency in the non-South, being white or female, and having an optimistic attitude about cancer prevention are all factors associated with greater knowledge of the tests, but not greater use among those aware of the tests. Membership in a health maintenance organization is more strongly associated with knowledge and use of fecal occult blood tests than the other tests. No association was found between current smoking status and knowledge of or use of any of the tests.