Blood was collected from bison that were selected between 1991 and 2001 for poor body condition, cachexia, lameness and balanoposthitis. Sera were tested for antibodies to bovine herpes virus type 1 (BHV-1), bovine viral diarrhoea virus (BVDV), foot-and-mouth disease virus (FMDV), parainfluenza virus type 3 (PI-3), Brucella abortus, Chlamydophila abortus, Coxiella burnetti, and Leptospira interrogans. The results of serological tests showed a prevalence of low titers of a serological reaction to Chlamydophila abortus (45.1%), bovine viral diarrhoea virus (29.5%), Leptospira interrogans (21.3%) and parainfluenza virus type 3 (13.9%). There were differences in the prevalence of antibodies to Ch. abortus between female and male bison. Futhermore, a relationship between age and antibodies to BVDV was observed in older bison. These results suggest that there is some transmission of bacterial and viral pathogens occurring between domestic and wild ruminants grazing in the same pastures in the peripherial areas of Bialowieza Primeval Forest.