The study reported here determined the prevalence of multiple sclerosis (MS) between January 1, 1998, and December 31, 2000, for a 19-county study area surrounding Lubbock, Texas. The primary data source for case ascertainment was medical records from the offices of neurologists practicing in the study area. The study found that the overall prevalence for the 19-county study area was 42.8 per 100,000 population (95 percent CI = 36.8-49.5). The prevalence estimate for females was 68.6 per 100,000 (95 percent CI = 58.0-80.6), and for males it was 16.6 per 100,000 (95 percent CI = 11.6-23.1). The prevalence estimate for non-Hispanic whites was 56.0 per 100,000 (95 percent CI = 47.1-66.1); the next highest prevalence was among non-Hispanic blacks at 22.1 per 100,000 (95 percent Cl = 8.1-48.1), and Hispanics at 11.2 per 100,000 (95 percent CI = 6.4-18.2). This project generated the first Texas-specific population-based MS prevalence estimates, including prevalence estimates specific to Hispanics and blacks in Texas. The results underscore the need for additional epidemiologic information on the distribution of MS in other areas of Texas and the United States, as well as information on the underlying etiology of the disease.