Pachinko is a popular form of recreation in Japan. However, in recent years, along with Pachinko's popularity, "Pachinko dependence" has become topical news. The purpose of this study was to investigate beta-endorphin, catecholamines, immune system responses and heart rate during the playing of Pachinko. The following significant results were observed. (1) Plasma concentration of beta-endorphin increased before playing Pachinko and while in the Pachinko-center (p < 0.05). (2) Beta-endorphin and norepinephrine increased when the player began to win (i.e. at "Fever-start") compared to baseline (p < 0.05). (3) Beta-endorphin, norepinephrine and dopamine increased when the winning streak finished (i.e. at "Fever-end") compared to baseline (p < 0.05-0.01). (4) Norepinephrine increased past 30 minutes after "Fever-end" compared to baseline (p < 0.05). (5) Heart rate increased before "Fever-start" compared to baseline, peaked at "Fever-start" and rapidly decreased to match rates measured at rest. But the increase was observed from 200 seconds after "Fever-start" (p < 0.05-0.001). (6) There was a positive correlation between the number of hours subjects played Pachinko in a week and the differences between beta-endorphin levels at "Fever-start" and those at rest (p < 0.05). (7) The number of T-cells decreased while the number of NK cells increased at "Fever-start" compared to baseline (p < .05). These results suggest that intracerebral substances such as beta-endorphin and dopamine are involved in the habit-forming behavior associated with Pachinko.