Background:Leptospirosis is a zoonotic disease and its incidence is known in Chile since 2002, when it was incorporated as a disease that must be reported to health authorities. A serologic survey for leptospirosis was performed in humans and animals from a farm in a semi urban area in Santiago Chile, after the death of a farmer due to Weil disease in that place. Aim: To report the prevalence of antibodies against leptospirosis and to determine exposure to infection risk factors in the humans and domestic animals studied in this survey. Material and methods: Antibodies were detected by IgM immunodot and indirect haemagglutination test in 61 humans (43 male, aged 5 to 70 years) and by microscopic agglutination test (MAT) in 44 animals. A questionnaire was applied to determine their exposure to risk factors for infection with Leptospira. Results: Seventy two percent of the studied population were farm workers and 70% had activities that required contact with water from canals, 41% cleaned closed places where rodents were present. Other risk factors detected were lack of sewage and waste disposal, high level of rodent infestation and disposal of faeces into canals used for watering. Two humans (3.3%) and six animals (1 bovine and 5 rodents) had positive antibodies. Among animals, antibodies against Leptospira serovar pomona and icterohaemorragiae were detected. Conclusions: In Chile, leptospirosis exists not only in rural areas but semi urban ones close to Santiago, although the prevalence is low. Education is necessary among semi urban population to avoid infection