cases of brasilian spotted fever (bsf) have been occurred since 1985, in the rural area of pedreira town, situated 160km away from the city of s？o paulo (longitude 46o54'07"; latitude 22o44'21"). aiming at evaluating the prevalence of brasilian spotted fever in this endemic area, single-serum samples were collected from 473 healthy persons, amongst city-dwellers and the local china industry workers. the obtained samples were tested by indirect immunofluorescence (ifa), in order to determine the antibodies titer for the group of brasilian spotted fever. twenty-five (5.3%) were considered positive (titer 3 1:64) and thirty-one (6.5%) were taken as "borderline" (titer 1:32). the results show a serologically positivity rate similar to other areas, known as endemic ones within the country.