The present work was conducted during 1996/1997 and 1997/1998 seasons to survey and study seasonal abundance ,of some dominant species of homopterous insects (aphids, leafhoppers and plan-thoppers) infesting citrus trees (Balady orange, Mandarin, Navel and Va‌lencia orange). Moreover, the effects of some climatic factors on the population density of these insect pests have been studied during the course of this investigation in different regions of Sharkia Governorate, Egypt. The following aphid species were collected; Aphis gossypii Glover, Aphis cmccivora Koch. Aphis citricola v.d. goot and Myzus persicae (Sulz‌er). During the years of investigation, two peaks of Aphis gossypii were recorded at mid of March and the end of July, respectively. Aphis citrico‌la had one peak at the end of March, while Aphis craccivora had also one peak at the end of February on Balady orange and Valencia orange. The collected leafhopper species were; Empoasca decedens (Pao‌li), Empoasca deapiens and Cicadulina chinai (Ghauri). Three peaks of Empoasea decedens were recorded at the end of October, end of May and at the end of September. Empoasca decipiens had one peak at the end of May, while Cicadulina chinai had two peaks at the end of October and at mid of September, respectively. The collected plant hopper species were; Sogatella farcifera (Horv.) and Sogatella vibix (Houpt), which had two peaks. The first was at mid of October and the second peak was at the end of September. The statistical analysis indicated that the effect of maximum and minimum temperature on the population of the studied insects was more than the effect of relative humidity.