Nine Egyptian cotton varieties were evaluated for their suscepti­bility to infestation with certain sucking insects under field conditions of north Delta during 1995 season. Weekly count of total number of in­sects per 25 seedlings or leaves chosen at random, showed that peak aphid populations on the different varieties occurred during the period from the 2nd week of July to the 3rd week of August. The highest num­bers of aphids existed on cotton variety Giza 83, while Giza 70 har­boured the least numbers. On the other hand, cotton variety Giza 83 was the least infested variety with jassids and whiteflies, which showed highest affinity to va­rieties Giza 70 and Giza 85, respectively. In most tested varieties, the total populations of the three suck­ing insects correlated positively with temperature, and relative humidity, while this correlation was negative with wind speed in all tested varie­ties. The combined effect of the three climatic factors was more pro­nounced on the populations on Giza 45 and Giza 80 than on other varie­ties since it was responsible for 86.8 and 80.33% of variability in the populations, respectively. On the other hand, the total populations were less affected by the three climatic factors collectively on Giza 76, Giza 83 and Giza 77, where it was responsible for 28.00, 21.75 and 19.80% of variability in the populations, respectively.