The work reported in this thesis fell into three main sections. The first was a study of the immunochemistry of a saline extract of T. saginata proglottids (SE) with particular reference to the antigens involved in the serological response of cattle to infection with T. saginata. It was hoped that this information would facilitate the production of relatively pure and specific T. saginata antigens for use in serodiagnostic tests for this infection. The second section was concerned with an investigation of the potential of certain serological techniques, not previously used with T. saginata infections in cattle, for use in serological investigations of experimental and field infections. In the third and final section these serological techniques were used to measure the serum antibody levels in cattle both experimentally and naturally infected with T. saginata. Where possible, partially purified saline extracts of T. saginata were used as antigens in these techniques. The immunochemistry of SE was studied by gel filtration on Sephadex G200, Sepharose 6B and Sepharose 42, by ion exchange chromatography and by immunoadsorption techniques. It was found that SE consisted of two main groups of antigenic molecules. The first group were of a molecular weight equivalent to that of the macroglobulin component of bovine serum and contained most of the haemagglutinin activity. The second group were of a molecular weight equivalent to that of the globulin component of bovine serum and contained mainly gel precipitin activity. The ismnnoadsorption studies on this extract showed the method to be potentially valuable for the purification of these helminth antigens but much work still remains to be done on this relatively new approach. The micro immuno-precipitation (MP) and the indirect haemagglutination (IDH) techniques had already been used in bovine cysticercosis research prior to the commencement of this work and only minor modifications have been made to these procedures. However, the haemagglutination inhibition (HI), enzyme-linked immunosorbent assay (ELISA) and the soluble antigen fluorescent antibody (SAFA) techniques have each been adapted to the study of the T. saginata system in cattle for the first time. A comparison of SAFA and ELISA showed that ELISA was the preferable of the two techniques for experimental work. The technique also has potential as a versatile and sensitive tool for studies on naturally infected cattle. The HI technique proved effective in detecting haemagglutinin activity in fractions of SH produced by column chromatography. Studies on cattle experimentally infected with T. saginata showed that the ELISA technique compared favourably with the IDH and MGP techniques. ELISA could in fact be used to detect an antibody response to both haemagglutinin and gel precipitin antigens. In contrast the IDH technique mainly detected an antibody response to haemagglutinins and the MP technique an antibody response to gel precipitin antigens. A limited study on cattle naturally infected with T. saginata showed, however, that ELISA is not presently a reliable test for T. saginata infection in the field. In particular, further work requires to be done on the antigens used in serological techniques, although there was an indication that some, but not all, cross reacting antigens could be removed by gel filtration and immunoadsorption.