Background: The purpose of this study was to develop and to evaluate the applicability of the Korean comprehensive geriatric assessment tools through reliability and validity testing. Methods: We developed standard and short-form assessment tools comprised of questionnaires on medical, functional, mental, socioeconomic status and lifestyle information and functional tests. The tools were administered as test-retest on 111 elderly outpatients at four university hospitals and two welfare centers in Seoul. Weighted kappa value, kappa value, Pearson’s correlation coefficients and overall percent agreement were calculated to evaluate reliability. Validity coefficient was estimated by using the reliability coefficient. Results: Reliability and validity coefficients were higher than 0.50 (fair or good) for 29 of 36 items. For test-retest reliability, the median was 0.66 (range, 0.29 to 1.00) for the kappa value and 0.83 (range, 0.53 to 1.00) for the Pearson’s correlation coefficients. Compared to the standard form, the short-form assessment questionnaires showed to be reliable and valid. Conclusion: The Korean Comprehensive Assessment Tools, both the standard form and the short form, were shown to be a reliable and valid screening medium for assessing the health status of the elderly in the ambulatory care setting. These instruments can be used conveniently for comprehensive outpatient geriatric assessment.