This investigation was carried out at Giza Experimental Station, Agricultural Research Center, during two successive growing seasons (2003-2004) to study the effect of pests and diseases infection on the yield, yield components and fiber quality of the Egyptian cotton varieties, Giza 80, Giza 83, Giza 90, Giza 85, Giza 88, Giza 89 and Giza 88 grown in pots having natural field soil. Data showed that there was no interaction between cultivar and treatment. The percentage of diseases infection was significantly affected by the treatment. Treatments (T3) 3 gmiKg monoceren seed treatment and (T4) 3 nKg gausho and monoceren seed treatment significantly reduced infection by 38.5% and 33.3%, respectively. Regarding to the cultivar, application of Gausho (T2) had no effect on the percentage of infection. These results indicate that application of seed-dressing fungicides was indispensable to protect seedlings against fungi involved in damping-off. Highly significant interactions were found between varieties and treatments for Aphids, while it was significant for whitefly. The Egyptian cotton varieties losses about 25.2 to 58.2% for the seed cotton yield due to pests. While it losses about 101% to 38.2% for seed cotton yield due to diseases. Giza 90 variety gave a highest tolerance than the other varieties against pests infection followed by Giza 83 and Giza 80, respectively. Diseases infection Giza 90 variety gave highest tolerance followed by Giza 89.