In patients with parasitologically revealed dermatitis caused by cercariae of avian schistosomes (Trichobilhariza szidati) diagnostic indirect immunofluorescence technique (IFAT) was employed for the detection of antibodies. The efficacy of antigens prepared from cercariae of T. szidati and Schistosoma mansoni was tested in serodiagnosis. The results have shown that antigen of T. szidati is more reactive with the sera of patients than that of S. mansoni: the antibodies were detected already 3 days after penetration of cercariae, contrary to 10 days after penetration of avian schistosomes when antigen of S. mansoni was used. The results were confirmed with enzyme-linked immunosorbent assay (ELISA) and IFAT techniques in SPF mice (Mus musculus) experimentally infected with cercariae of T. szidati and S. mansoni or with fractions isolated from cercariae of T. szidati.