Indirect ELISA techniques for the detection of antibodies to S. bovis serotypes 1, 2 and 3 in pigeon plasma were developed. Whole formaldehyde-inactivated bacteria were used as coating antigens. Bound antibodies were detected with peroxidase-conjugated rabbit anti-pigeon serum and OPD and H2O2 as chromogen and substrate, respectively. ELISA was used to determine the prevalence of antibodies to S. bovis serotype 1 in healthy Belgian racing pigeons. Antibodies were demonstrated in 83 (= 37%) of 225 samples tested. Results indicate that pigeons may build up plasma antibodies in the absence of clinical signs resembling septicaemia.