Systematic and effective means for promoting and protecting the welfare of the disabled requires reliable criteria that accurately demonstrate the presence and measure the severity of the disability. Given the same disability, however, the degree of that disability may measure differently according to the particular criteria used in Korea. In addition to inconsistency, the varying set of criteria has resulted in significant diagnostic errors, fraud, and malingers, leading to overall distrust and dissatisfaction. Accurate disability evaluation is the key for the welfare for the disabled. Evaluation of the physical impairment is possible only by the medical doctors. Doctors should know the concept, purpose, and methods of disability evaluation.