This research analyzes similarities and differences in how students with disabilities are identified in national databases, through examination of 19 national data collection programs in the U.S. Departments of Education, Commerce, Justice, and Health and Human Services, as well as databases from the National Science Foundation. The study found that significant variability was evident in the disability categories used both within and across the national data collection programs. The variability was found in the use of terms that corresponded to the federal categories of seriously emotionally disturbed, hard of hearing, deaf, visually handicapped, orthopedically impaired, and other health impaired. The disability category for which there was the greatest similarity of terms across the largest number of data collection programs was speech impaired. Suggestions are provided for improving disability identification in collecting and reporting policy-relevant information. Appendixes provide tables indicating correspondence among federal disability categories and categories used in national data collection programs, and outlines examples of new variables to be considered to better describe those individuals who are included or excluded in data collection programs. (Contains 13 references.) (JDD)