In October 1997, the U.S. Office of Management and Budget announced new government-wide standards for the collection of data on race and ethnicity (published as U.S. OMB 1999) effective January 1, 2003. Previously, racial/ethnic groups were identified as white, non-Hispanic; black, non-Hispanic; Hispanic; Asian or Pacific Islander; and American Indian or Alaskan Native. Because the old standards were in effect when the data for this report were collected, the racial/ethnic groups described here are designated by the old standards. Where data collection permits, subgroups of the Hispanic population are identified (e.g., Mexican, Puerto Rican). Data on people in science and engineering who have disabilities are seriously limited for several reasons. First, the operational definitions of "disability" vary, include a wide range of physical and mental conditions, and thus are not totally comparable. Second, data on disabilities frequently are not included in comprehensive institutional records (e.g., in registrars' records in institutions of higher education). If included at all, such information is likely to be kept only in confidential files at an office responsible for providing special services to students. Third, information about people with disabilities that is gathered from surveys is often obtained from self-reported responses. The attempt to provide estimates of the proportion of the undergraduate student population with disabilities is an example of how these factors coalesce. Self-reported data on the undergraduate student population, collected through a survey to ascertain patterns of student financial aid, suggest that about 10 percent of this population have a disability. Estimates from population surveys of higher education institutions, in contrast, place the estimate much lower, between 1 and 5 percent. Whether this discrepancy is the result of self-perception, incomplete reporting, nonevident disabilities, or differing definitions is difficult to ascertain. In the final analysis, although considerable information is available about the number of individuals with disabilities in the education system and in the science and engineering workforce, it is often impossible to compare statistics from different sources. This report presents information about the participation of women, minorities, and persons with disabilities in science and engineering education and employment for 2004. (Contains 20 figures and 107 tables.)