From December 1994 to February 1995, 131 wild boars (Sus scrofa leucomysta) living in a mountainous area in Japan were examined for yersiniosis and listeriosis. Of 131 wild boars, 76 (58%) were males and 55 (42%) were females. Four Yersiniaspp. including Y. pseudotuberculosis, Y. enterocolitica, Y. frederiksenii,and Y. aldovei,were isolated from 49 (37%) of 131 wild boars. Yersinia pseudotuberculosiswas isolated from five (4%) of 131 wild boars. All Y. pseudotuberculosisisolates were serotype 4b and harbored virulence plasmids. Yersinia pseudotuberculosiswas isolated only from boars under 2-yr-old. No human pathogenic Y. enterocoliticawas isolated. Listeria monocytogeneswas isolated from two (1%) of the wild boars and both isolates were serotype 4b. These findings indicated that wild boar could be a reservoir of Y. pseudotuberculosisand L. monocytogenesin Japan.