This study tested the validity and reliability of a written test designed to assess knowledge of coronary heart disease (CHD) and its risk factors. The subjects were 93 males diagnosed with CHD. Subjects were classified into a treatment group (n = 48) or a control group (n = 45) based on whether or not they participated in a cardiac rehabilitation program (CRP). An additional 38 subjects were used to pilot test the original form of the knowledge test, which consisted of 80 multiple-choice questions. Content validity was established by a five-member jury of cardiac rehabilitation experts. Each question was rated using a Likert-type scale. Questions that did not receive an average rating of at least four were eliminated. The revised form was pilot tested for validity and internal consistency with the discrimination index (point biserial correlation coefficient) and the Kuder-Richardson formula 20 (KR-20). Questions with a discrimination index of less than 0.14 were eliminated; thus, the final form of the test consisted of 40 questions. Validation of this test yielded difficulty ratings (DRs) between 0 percent and 98 percent, with an average DR of 63 percent. Construct validation indicated that the average test score of subjects participating in a CRP was significantly higher than that of non-participants (t = 3.51, df = 91, p ≤ 0.01). The internal-consistency reliability of the test was 0.84. The results indicate that this test is a valid and reliable tool for assessing patients' knowledge of CHD and its risk factors.