The aims of our study were to assess the validity and reliability of a telephone survey instrument designed to measure vascular disease risk factors and to assess whether these measurements were influenced by age, gender, race/ethnicity, or other sociodemographic variables. Subjects were sampled and interviewed using random digit dialing methodology from the multiethnic community of northern Manhattan. For the validity study, 261 consecutive subjects were clinically assessed in-person within 60 days of the telephone interview. A retest reliability study of the telephone interview was conducted in 92 randomly selected subjects within 30 days of the initial interview. The telephone interview instrument had a sensitivity of more than 55% and a specificity of 74% or greater for various vascular disease risk factors. Sensitivity, specificity, and positive predictive value did not vary significantly or systematically among whites, blacks, and Hispanics, but subjects with access to health care were more likely to provide valid data. The reliability substudy indicated a good reliability for the telephone interview. These results support the validity of telephone interviews for estimating the prevalence of vascular risk factors in urban populations.