In order to investigate seven cotton varieties i.e. Giza 86, Giza 94, Giza 87, Giza 88, Giza 92, Giza 93 and Giza 96 under 14 environments (seven locations i.e. Alexandria, Damnhour (El-Beheira), Edko (El-Beheira), Kafr El-Sheikh, Sedi Salim (Kafr El-Sheikh), Kafr Saad (Damietta), Kafr El-Batekh (Damietta) under two successive seasons, 2013 and 2014 to study the evaluation, adaptability and stability in the performance of different environmental conditions for seed cotton yield. the variety x environment mean square was significant, indicating different response of the varieties in different environments. Regression of seed cotton yield on the ecological index depicted changes betweenthe verified varieties for yield stability and flexibility. Varieties Giza 87, Giza 92 and Giza 96 produced the highest seed cotton yield with regression coefficient did not differ unity (b_i-1) and were documented as highly modified to all the environments. Also, genotypes had deviation from regression equal zero (S²d_i=0). Furthermore, Giza 94 was lowly adapted to all the environments where regression coefficient apart from one and (S²d_i ≠ 0) so, it is more sensitive to any change in the environmental conditions, considered as high yielding environments and unstable.