The zoonotic cestode, Taenia saginata is cosmopolitan in its distribution but the prevalence is greater in the tropics and sub-tropics. The parasite causes public health problems and production losses due to condemnation of infected carcasses or down-grading of carcass value. The development of specific diagnostic procedures and the preparation of vaccines would greatly aid the control of the parasite. Diagnostic and protective antigens have already been described in the parasite oncosphere stage [2,3]. In order to study such relevant antigens, a T. saginata oncosphere cDNA library was prepared in hUni-Zap-II (Stratagene Ltd) from 1.2 ug of mRNA isolated from 3 x lo6 hatched and activated oncospheres.