The redback spider, Latrodectus hasseltii, which is widely distributed throughout tropical and temperate regions worldwide was not known in Japan until it was collected and identified in Osaka Prefecture in the fall of 1995. Since then, many redback spiders were found in Osaka and Mie Prefectures. The field investigation showed that these spiders distribute in extensive areas of Osaka Bay and Yokkaichi Port in Japan. The tolerance to low temperature was tested with redback spiders collected in the above areas by individual rearing in glass flasks at 5-25℃ (10L : 14D) in laboratory. They showed appreciable cold tolerance and they also tolerated well to a high temperature (40℃). These findings suggest the possibility of the distribution of redback spider in wider areas in Japan in the near future and occurrence of lactrodectism in this country.