Cancer screening is a national health priority, especially for colorectal cancer, the second leading cause of death due to cancer in the United States. The researchers measured colorectal cancer knowledge among 211 older Americans. A quasiexperimental pretest-posttest two-by-two factorial design was used to test the effect of knowledge on participation in fecal occult blood screening. The American Cancer Society's colorectal cancer educational slide-tape presentation served as the basis for all of the educational programs. Hemoccult II kits were distributed at no cost to the participants. Descriptive statistics, chi 2, and logistic regressions were used to analyze data. One-half of the participants had incomes below the poverty level. Almost one-half the subjects in the study sample stated that they had not received any information about colorectal cancer within the past year. Caucasians had more knowledge of colorectal cancer than African Americans [F(1, 78) = 7.92, p < 0.01] and persons with higher income had more knowledge than persons with less income [F(2, 76) = 3.01, p = 0.05]. Subjects showed significant increases in colorectal cancer knowledge 6 days after the colorectal cancer education program [t(79) = 2.59, p = 0.01] and this increased knowledge was a predictor of participation in free fecal occult blood screening [chi 2(1, n = 164) = 5.34, p = 0.02].