Arthritic joints obtained from 50 freshly slaughtered pig carcasses condemned for polyarthritis were studied microbiologically. A routine technique was developed for aseptically opening joints to obtain material for microbiological examination. A standard series of culture media for the primary isolation of arthritogenic agents were used in the examination of each affected joint. The microbiological study cultured for isolation of the following microorganisms: Erysipelothrix rhusiopathiae, Corynebacterium pyogenes, Staphylococcus aureus, Escherichia coli, Streptococcus spp., Haemophilus spp., Mycoplasma spp., Salmonella spp., Chlamydia, and viruses.E. rhusiopathiae was found to be responsible for 48% of the cases of arthritis and Streptococcus spp., C. pyogenes and S. aureus for 20%, 4%, and 2% respectively; no microorganisms were cultured from 26% of the arthritic joints.