This paper reviews research conducted on the link between pathological gambling and substance misuse. We first examine the phenomenon of "pathological gambling," including similarities between pathological gambling and substance misuse, instruments used to measure pathological gambling, and the prevalence of pathological gambling in the United States and internationally. We then examine research on substance misuse among pathological gamblers, pathological gambling among substance misusers, and the treatment of the pathological gambler-substance misuser. We conclude with a discussion of future research needs.