Field work and experiments were conducted at Shandaweel Experimental Station at Souhag Governorate, during 2015-2018 seasons. In 2015 season, sixty type plants were selected from the breeding nursery of Giza 90 cotton cultivar that produced sixty progenies (increase A) in 2016. From the latter, 17 families were selected to form (increase B) in 2017, nine elite families were selected and their seed were massed carefully together to form the nucleolus (Breeder's seed) in 2018 season. The results obtained here indicated that, the pure line method in the sense of pedigree selection for annually renewing Giza 90 breeder's seed could prevent genetic contamination. Meanwhile, the selection technique for producing breeder's seed of Giza 90 cultivar was valid and proved to be effective in holding the true type of the variety.