There is considerable debate about the appropriate conceptualization of pathological gambling and its place in psychiatric nosology. The authors examined the existing research on different areas of pathological gambling to find evidence for a particular model of this disorder. There are 2 dominant models of pathological gambling: as a nonpharmacologic addiction and as an obsessive-compulsive spectrum disorder. The data available from different areas seem to converge in suggesting that pathological gambling has characteristics that are similar to those of substance abuse, and less close to those of obsessive-compulsive disorder, although those conceptualizations are not mutually exclusive. An alternative model of pathological gambling is that it constitutes a heterogeneous disorder with some subtypes resembling obsessive-compulsive disorder, and other subtypes being closer to substance abuse disorders. Improved understanding of the conceptualization of this disorder may help improve the quality of the treatments available.