A particularly rapid onset of pathological gambling (PG-onset) through the use of gambling machines has been widely alluded to, but this is the first study to empirically examine the phenomenon. This study compared the latency of PG-onset in those who gambled primarily on machines, compared to those who gambled primarily on more "traditional" forms of gambling at PG-onset. Subjects were 44 adult pathological gamblers (PGs) seeking outpatient treatment in Rhode Island (17 females; mean age = 46.9). Subjects completed questionnaires and a diagnostic interview including a complete history of gambling activities and the course of PG. The "latency" of PG-onset was defined as the time (in years) elapsed between the age of regular involvement in the primary form of gambling and the age at which DSM-IV criteria were first met. "Machine" PGs (n = 25) had a significantly shorter latency of onset than did "traditional" PGs (1.08 years vs. 3.58 years). Females and machine PGs had a significantly older age of onset, but gender was not associated with latency of PG-onset. Lifetime comorbidity of either substance use disorders (SUDS) or depressive disorders (DDS) was also not associated with the latency of PG-onset. The results of the current study suggest that intrapersonal variables such as gender and comorbid disorders do not generally affect the speed with which people develop PG. Rather, the social, environmental, and stimulus features of mechanized gambling are implicated. Prospective longitudinal studies on the onset and course of PG are needed, as well as more basic research on the features of machine gambling that may contribute to rapid onset.