4 Egyptian mosquito species were tested for their ability to transmit the Egyptian ZH-501 strain of Rift Valley fever virus (RVFV) to golden Syrian hamsters. Culex (Cx.) antennatus was the most efficient vector, showing a 37.5% transmission rate following a hamster blood meal containing 10 suckling mouse intracerebral 50% lethal doses (SMILD50) per ml. Fully engorged mosquitoes of this species showed an infection rate of 85% with the mean viral titres of transmitting mosquitoes 100-fold higher than non-transmitters. Autogenous and anautogenous populations of Aedes (Ae.) caspius were tested separately, and the transmission rates were 23.1% and 9.7% respectively, following feeding on hamsters with similar levels of viraemia. Two anopheline species, Anopheles (An.) multicolor and An. pharoensis, showed 12.5% and 3.5% transmission rates under similar conditions. In these 3 species infection rates exceeded 75% and mosquitoes transmitting had a higher average titre than those not transmitting.