The percentage infection rates of Trypanosoma vivax in G. morsitans morsitans maintained after the infected meal on a cow, goats, rabbits, rats or mice were 88.0, 86.7, 94.8, 76.4 and 6.1, respectively. There were no significant differences between the males and females in this respect. The mortality rates of the tsetse maintained on mice or sheep were relatively high; the infection rate of the few survivors (5%) maintained on the latter host was 44.4%. The rates of T. congolense infection in the vector maintained on different hosts after the infected blood meal also differed. Goats (infection rate, 12.6%) and rabbit (11.4%) proved superior as maintenance hosts while rats (2.8%) and mice (0%) were inferior; sheep (7.8%) and cow (6.5%) were intermediate. The mortality rate of the tsetse maintained on mice and sheep was markedly high; the reasons for this are discussed. Whereas cows (11.5%) and rabbit (11.2%) were efficient hosts for maintaining tsetse after the T. brucei infected feed, rats (4.1%) were inferior. Goat (9.0%) and mice (7.6%) proved intermediate. The rabbit is probably the best host for maintaining tsetse after infected feeds since the infection rates of all 3 Trypanosoma spp. in the vector were quite high, and this host is also relatively easy to handle in routine feeding of tsetse.