Objective: Although pathological gambling has serious personal and societal consequences, little empirical research has been conducted on this subject in Japan. The purpose of this study was to more fully elucidate the characteristics of pathological gamblers in Japan. Methods : A retrospective examination of the medical records of 105 pathological gamblers（mean age: 38.9 years ; male: 79%） treated at a psychiatric institution was performed. Several factors were analyzed : sociodemographics ; gambling behavior and associated complications ; family history; and childhood maltreatment. Results : The mean educational duration was 12.8 years, 18% of the patients were divorced, and 23% were unemployed. Their high education and divorce rates were significantly greater than normal. Furthermore,30% of the patients suffered from depression, 18% were alcoholics, 48% had a family history of mental illness（addiction, 32% ; mood disorder,12%）,38% grew up in dysfunctional families, and 54% started gambling when they were in their teens. Female patients started gambling significantly later than male patients, but there were no significant differences in the onset of their illness in relation to their duration of gambling between males and females. Over 20% of the patients had lost control over their gambling habits within 2 years of their starting to gamble. In addition,91% of the patients played pachinko, a Japanese machine which is similar to a slot machine. Additionally, 95% of the patients had debts, and 34% had gone bankrupt. The total amount of debt owed was significantly correlated with the duration of this disorder. Conclusions : This study describes several characteristics of pathological gamblers in Japan. In particular, the author determined that many patients started gambling at a young age, and the duration of pathological gambling was significantly correlated with the amount of debt owed. These findings show the importance of the prevention and early detection of pathological gambling.