Abstract The stable fly, Stomoxys calcitrans (Linnaeus), and the yellow fever mosquito, Aedes aegypti (Linnaeus), were utilized to determine their capability to transmit Eperythrozoon suis Splitter between swine. Three groups of each insect in each trial were allowed to feed on a pig previously infected with E. suis and then transferred to susceptible splenectomized pigs. As a control, one group of each insect was fed on a non-infected pig and then transferred to a susceptible pig. Stable flies were transferred immediately and following a delay of 1, 4, 24 h and 7 days. Aedes aegypti were transferred immediately and following a 7 day delay. Successful transmission was accomplished in three of 15 pigs to which stable flies were transferred immediately and in nine of nine pigs to which A. aegypti were transferred immediately. No pigs became infected when there was a delay before transfer to the susceptible pig. All controls remained non-infected. This indicates that the stable fly and A. aegypti are likely to be mechanical vectors of E. suis under natural conditions. Differences in vector efficiency may be due to differences in mechanisms of blood-feeding which could affect the placement of the inoculum of E. suis.