Abstract Aims To examine differences between early-onset versus later-onset pathological gamblers in socio-demographic characteristics, rates of Axis I and II disorders, preferred type of gambling and rates of treatment-seeking in a large nationally representative survey of adults in the United States. Design Data were collected from face-to-face interviews using the Alcohol Use Disorder and Associated Disabilities Interview Schedule DSM-IV version IV (AUDADIS-IV). Setting and Measurement The study drew on data from the United States' National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Participants All individuals with a DSM-IV diagnosis of pathological gambling (PG). To be consistent with prior studies, age of onset of PG was dichotomized as 25 years and younger (early-onset) versus 26 years and older (later-onset). Findings Individuals with early-onset PG were more likely than individuals with later-onset PG to be male [odds ratio (OR) = 2.86; 95% confidence interval (CI) = 1.20, 6.82], never married (OR = 3.51; 95% CI = 1.39, 8.84), to have income below US$70 000 (OR = 0.09; 95% CI = 0.01, 0.61), to belong to younger cohorts (OR = 0.93; 95% CI = 0.89, 0.97) and to have a cluster B personality disorder (OR = 4.11; 95% CI = 1.77, 9.55), but less likely to have a mood disorder (OR = 0.42; 95% CI = 0.19, 0.94). There were no differences between individuals with early- and later-onset PG regarding rates of treatment-seeking (OR = 0.71; 95% CI = 0.20, 2.43) or preferred type of gambling (OR = 2.00; 95% CI = 0.55, 7.3). All results remained significant after adjusting for age, sex and race, except the difference in the prevalence for mood disorders, which was no longer significant. Conclusions Individuals with early-onset versus later-onset pathological gambling differ in several socio-demographic and clinical characteristics, but not in their preferred types of game. Individuals from more recent cohorts appear to be at significantly increased risk for developing early-onset pathological gambling.