The only non commercial reagant necessary to process the indirect-ELISA Trypanosoma species is the trypanosome antigen. Production of trypanosomes for indirect-ELISA is generally made in rodents. Rare T. vivax strains have been adapted to rodents, and, moreover, irradiation of the rats is often necessary to produce high parasitaemia in order to prepare antigens for indirect-ELISA. Production of such antigens is a limiting factor for most of the laboratories. T. evansi grows easily in mice with very high spontaneous parasitaemic levels and is known to have antigenic similarities with other salivarian trypanosomes. For these reasons, the utilisation of T. evansi antigens in the diagnosis of T. vivax infections could be an interesting alternative for laboratories which cannot produce T. vivax antigens. Qualitative studies in western blotting, and quantitative studies in indirect-ELlSA T. vivax and indirect-ELISA T. evansi have been conduced with sera from sheep experimentally infected with T. vivax or with T. evansi. The quantitative study in indirect-ELlSA with the antigens of T. vivax showed strong responses in homologous system (with sera from sheep infected with T. vivax), but low responses in heterologous system (with sera from sheep infected with T. evansi). On the contrary, with T. evansi antigens, the heterologous and homologous systems both give strong responses. It is therefore suggested that T. evansi antigens could be use in indirect-ELISA to detect both infections, and that positive samples to that test be tested with indirect-ELISA T. vivax# to allow distinction of the infection by one another parasite.