Cat scratch disease (CSD), bacillary angiomatosis, hepatic peliosis and some cases of bacteraemia, endocarditis, and osteomyelitis are directly caused by some species of the genus Bartonella. The purpose of this study was to determine the prevalence of IgG antibodies against Bartonella henselae in healthy people and to identify the epidemiological factors involved. Serum samples from 218 patients were examined by indirect immunofluorescence assay (IFA). Significance levels for univariate statistical analysis were determined by the Mann–Whitney U test, χ2 test and Fisher's exact test. Of 218 patients, 99 were female and 119 male, with a median age of 34·36 years (range 0–91 years). Nineteen (8·7%) reacted with B. henselae antigens. Of all the factors concerning the seroprevalence rate being studied (age, sex, contact with animals, residential area), only age was statistically significant. Our serological data seems to indicate that B. henselae is present in Catalonia and could be transmitted to humans.