The aim of the study was to investigate the occurrence of serum antibodies to C. psittaci in workers at 8 stock farms located in a rural area of eastern Sicily. Serum samples from 188 workers and 160 controls were tested for immunoglobulin IgA, IgG and IgM direct against C. psittaci by microimmunofl uorescent test (MIF). Seropositive subjects were defi ned as those with IgG titres of 1:16-1:256, and seronegative subjects as those whose titre was <1:16. To rule out the presence of cross reactive antibodies, testing was also performed for C. trachomatis and C. pneumoniae. A total of 28 (14.9%) subjects studied met the criteria for seropositivity to C. psittaci. Two of the 188 (1.06%) had an IgG titre of 1:32, 16 (8.51%) an IgG titre of 1: 64, 6 (3.19%) an IgG titre of 1:128 and 4 subjects (2.12 %) demonstrated an antibody titre of 1:256. The high prevalence rate of C. psittaci antibodies among farmers suggests that this infection is spread in those subjects living in areas with an high percentage employed in rearing activities. The authors stress the importance of carrying out health surveillance in subjects working in close contact with animals receptive to infection, and confi rm the need to adopt a serological test, such as MIF as a preventive measure for activities at risk.