Field experiments were conducted in Qalyubia governorate during two successive seasons 2007 and 2008 to study the population dynamics of some pests infesting Nili cucumber plantations namely Empousca decipiens (Paoli), Aphis gossypii (Glover), Bemisia tabaci (Genn) on two cucumber cultivars. Also the effect of certain weather factors (daily mean temperature, daily mean R.H.) and plant age were studied on the population dynamics of the various pests. The results revealed clearly no significant differences in the susceptibilities of the two cucumber cultivars (Hageen eshrak and Amira) to infestation with the above mentioned pests of cucumber plants during the two seasons. The weather factors (mean Temp. and plant age) had significant effect on the population dynamics of E. decipiens, A. gossypii and B. tabaci for the two cultivars. On the other hand the relative humidity had shown no significant effect on population dynamics of the three pests during the two seasons of 2007 and 2008 on the two cultivars. The percentage of variance was 92.7 & 84.5% and 98.6 & 94.2% for the two cucumber cultivars, during the two seasons, respectively. This means that the weather factors and plant age are responsible for about 92.7 in the variability of the populations of the observed pests on Hageen eshrak and 84.5% for Amira during 2007. The corresponding values during 2008 were 98.6 and 94.2% for the two cultivars, respectively.