This chapter focuses on the empirical, data-driven research pertaining to the public health issue of whether or not gambling expansion significantly alters the prevalence rate of disordered gambling and how this research can inform responsible gambling policies and practices. It is a legitimate public health concern that the expansion of gambling opportunities will contribute not just to increases in the prevalence rate of those who gamble and in gambling involvement (e.g., number of days gambling) but also to an increase in the rate of disordered gambling. This latter point is the central issue of this chapter. The authors rely on recent and peer-reviewed publications, although at times “gray” publications (i.e., government reports not in the peer-reviewed literature) are included.