Aphids are one of the most injurious insect pests infesting medic­inal and aromatic plants in Egypt. During vegetative stage, coriander was infested with three aphid species, namely Aphis gossypii Glover, Rhopalosiphum maidis Fitch. and Myzus persicae Sulzer, while caraway plants were attacked by only M.persicae. During the flowering and fruiting stages coriander and cara­way were infested also with Hyadaphis corianri Das. On the other hand, no aphids were observed on geranium plants. Statistical analysis showed that the temperature had a negative effect on the population of Myzus persicae Sulzer, while relative humidity have a positive effect. Thus, this species perferred low temperature and high humidity. On the contrary, the population density of Hyadaphis coriandri Das and Aphis gossypii Glo­ver, were positively correlated with the temperature, while the relative humidity had a negative effect on the aphid population density.