The protein pattern of Trichuris chilensis obtained by sodium dodecyl sulfatc-polyacrylamide gel electrophoresis was analyzed. Complex protein band patterns covering a wide range of molecular weights were obtained. The molecular weights of the major proteins present in different tissue homogenatcs were estimated. Antisera raised in rabbits against homogenates of T. chilensis and sera from naturally infected Ctenomys australis were used in Western blotting, Immunoelectrophoresis and passive hemagglutination to compare the antigenicity of the adult male, adult female, eggs, oocytes, stichosome and cuticle of this parasite. Specific antibodies to parasite antigens were also detected in faecal preparations and caecum mucosal extracts of C. australis naturally infected with T, chilensis.