Given the increasing interest in Lyme borreliosis in our community, and the lack of epidemiological studies in our country, we have considered convenient to analyze the presence of anti-Borrelia burgdorferi antibodies in a group of workmen who we have considered at high risk since they carry out their everyday work in an environment infested by ticks. Significant antibody titers (= or greater than 1/128) are found in 38% of cases versus 0% in the control group. The significance of these results in relation to the presence or not of compatible clinical manifestations and tick bites are studied.