Purpose: The purpose of this article is to determine the performance of a reactive hyperemia test in the general population in terms of validity, increase in case identification, and test refusal; and to identify differences between the two major ways of expressing the results (the postoccclusive ankle index and the percentage change in ankle systolic pressure). Methods: Changes in ankle pressures were measured during reactive hyperemia in 1460 men and women aged 55 to 74 years, who were randomly sampled in the Edinburgh Artery Study. The validity of the test was determined in 91 cases identified by the presence of intermittent claudication and a low resting ankle pressure and in 91 controls matched by age and sex. Results: The mean postocclusive ankle index was 0.98 (SD 0.20), and the mean drop in ankle pressure was 9.89% (SD 12.79%). In examining the validity of the test, differences occurred in the two ways of expressing the results: the postocclusive ankle index was 90% sensitive and 97% specific and the percentage drop in ankle pressure was 52% sensitive and 86% specific in detecting disease. The postocclusive ankle index increased the overall identification of cases in the Edinburgh Artery Study from 6.5% to 11.5%, but the percentage drop in ankle pressure increased identification to only 9.5%. Eight percent of subjects refused the test because of discomfort; this group contained more women, more elderly, and more obese subjects. Conclusions: The reactive hyperemia test is an appropriate test to use in the general population. The results are more accurate when expressed as the postocclusive ankle index rather than the percentage drop in ankle pressure.