BACKGROUND: Little is known about the prevalence or correlates of DSM-IV pathological gambling (PG). METHODS: Data from the US National Comorbidity Survey Replication (NCS-R), a nationally representative US household survey, were used to assess lifetime gambling symptoms and PG along with other DSM-IV disorders. Age-of-onset (AOO) of each lifetime disorder was assessed retrospectively. AOO reports were used to study associations between temporally primary disorders and the subsequent risk of secondary disorders. RESULTS: Most respondents (78.4%) reported lifetime gambling. Lifetime problem gambling (at least one Criterion A symptom of PG) (2.3%) and PG (0.6%) were much less common. PG was significantly associated with being young, male, and Non-Hispanic Black. People with PG reported first gambling significantly earlier than non-problem gamblers (mean age: 16.7 vs. 23.9, z = 12.7, p=.001), with gambling problems typically beginning during the mid-20s and persisting for an average of 9.4 years. During this time the largest annual gambling losses averaged $4800. Onset and persistence of PG were predicted by a variety of prior DSM-IV anxiety, mood, impulse-control, and substance use disorders. PG also predicted the subsequent onset of generalized anxiety disorder, post-traumatic stress disorder, and substance dependence. Although none of the NCS-R respondents with PG ever received treatment for gambling problems, 49.0% were treated at some time for other mental disorders. CONCLUSIONS: DSM-IV PG is a comparatively rare, seriously impairing, and under-treated disorder whose symptoms typically start during early adulthood and is frequently secondary to other mental or substance disorders that are associated with both PG onset and persistence.