Field studies had been carried out in peach orchard at Mansoura district to investigate the population fluctuations of the Bemisia argentifolii Bellows and Perring and the leafhoppers attacking peach trees and their associated predatory insects during the two successive years (2005 and 2006). In addition, we evaluated the effect of temperature and relative humidity on the population densities of these insects under field conditions.                                                                               The obtained results indicated that there were four insect species belonging to Order Homoptera attacking peach trees. These insect pests were B. argentifolii ; Empoasca discipiens  Poali ; Empoasca lybica de Berg and Agallia aegyptiaca Host. Also, two predators were associated with these insect pests. These predators were Chrysoperla carnea (Steph.) and Exochomus nigromaculatus (Goeze). The data indicated that A. aegyptiaca was first record on peach trees at Mansoura district. Data revealed that B. argentifolii had four peaks on peach trees in the two years of study. The highest peak was recoded in the second week of September in 2005, while that was in the second week of October in 2006. The results showed that temperature had highly positive significant effect on the population densities of this insect. On the other hand, the maximum relative humidity had positive significant effect.    The obtained results recorded that E. discipiens had five peaks on peach trees in the first year. Whereas, there were three peaks in the second year of study.  The highest peak was found in the third week of July in the two years of study. The statistical analysis showed that temperature components had positive significant effect on the population densities of this insect, while the maximum relative humidity had greatly effect.    The results indicated that E. lybica had five and four peaks in 2005 and 2006, respectively. The statistical analysis showed that the temperature had positive significant effect on the population density of this insect. On the other hand, the maximum relative humidity had greatly effect on the population density of  this insect.    The results indicated theA.aegyptiaca had four peaks in the first year, whereas five peaks in thesecond year. The statistical analysis of maximum, minimum andaverage temperature had highly effect on the population density of this insect, while the maximum relative humidity had greatly effect on the population density of this insect. The results showed that E. nigromaculatus had three peaks in the first year. Whereas, five peaks were recorded  in the second year of study, while C. carnea had four peaks in the two years of investigation.