Vector competence of Glossina pallidipes for pathogenic Trypanosoma species was compared to that of G. morsitans centralis. Cattle or goats were the hosts used to infect teneral tsetse, rabbits were used to maintain tsetse which were dissected on day 30. Mean infection rates of G. pallidipes and G. m. centralis by T. vivax isolated from a cow in Kenya were respectively 39.5 +/- 8.9% and 32.1 +/- 10.3% whilst for T. vivax isolated from a cow in Nigeria, they were 30.0 +/- 7.5% and 19.8 +/- 4.3%. Differences were not significant. Differences in infection rates between the sexes of flies were also not significant. Transmission capability to goats by either tsetse species was good for the two T. vivax isolates. Mean infection rates by T. congolense isolated from a lion in Tanzania were significantly lower in G. pallidipes (8.5 +/- 1.8%) than in G. m. centralis (22.5 +/- 2.0%). Males of either tsetse were more susceptible than females. Transmission rates to goats and mice by both tsetse species was 100%. G. pallidipes (3.5%) was less susceptible than G. m. centralis (25.1%) to T. congolense isolated from a cow in Nigeria, but transmission rates to goats and mice by either tsetse was 100%. Also, G. pallidipes (2.7 +/- 0.4%) was significantly less susceptible than G. m. centralis (18.4 +/- 1.1%) to T. b. brucei isolated from a hartebeest in Tanzania. Males of either tsetse species were more susceptible than females. Transmission rates to goats and mice by either tsetse was 100%. G. pallidipes (0%) was not susceptible to T. b. brucei isolated from a pig in Nigeria whilst G. m. centralis showed infection rate of 9.3%. When male G. pallidipes and G. m. centralis were fed every day for 27 days on a goat infected with this T. b. brucei from Nigeria, the infection rates were 8.7% and 20.2%, respectively. Transmission rates to mice by either tsetse species was 100%. In conclusion, G. pallidipes has a vector competence equal to that of G. m. centralis for T. vivax, whilst G. pallidipes has lower vector competence than G. m. centralis for T. congolense and T. b. brucei.