We examined the sera of 587 hunters in Hokkaido (Japan’s northernmost island) for the antibody to Borrelia burgdorferi (B. burgdorferi) by enzyme immunoassay, clarified the conditions related to antibody positivity in these subjects according to region, and studied the effects of factors such as age and lifestyle on the antibody titer. In contrast with an anti-B. burgdorferi antibody positive rate of 7.1% in control sera, that in the hunters’ sera was 16.0%. Among those positive for the anti-B. burgdorferi antibody, the antibody positive rate in sera excluding those testing positive in the serological test for syphilis was 5.5% in the controls, and 15.4% in the hunters, the latter rate being significantly higher (p less than 0.05). In both hunters and control groups, the antibody-positive rate tended to be higher in older subjects, but the antibody titer showed no correlation with their age, or the duration of their hunting experience. Examination of the hunters’ occupations revealed a tendency toward high titers in those engaged in dairy farming. The antibody positivity of those who went gathering edible wild plants was significantly higher than those did not (p less than 0.05). These observations suggested that the high antibody-positive rate in hunters may have been due largely to the effect of activities other than hunting as sources of infection by Borrelia.