The rapid expansion of legalized gambling in the United States has produced tremendous demands for information about the number and characteristics of problem gamblers in the general population. This paper examines the results of prevalence studies of problem and pathological gambling that have been carried out in the United States. The discussion is largely chronological, with a focus on comparative findings from the 15 United States jurisdictions where prevalence studies have been completed since 1980. The results of diese studies verify findings from clinical and experimental studies as well as suggesting important avenues for future research. The paper concludes with a consideration of the role played by survey research in advancing the field of gambling research.