Two pot experiments were conducted at the Agricultural experimental station of ARC in Giza to study the effect of irrigation with saline water on growth, yield as well as pigments, total soluble sugars, reducing sugars and proline contents in leaves, oil and protein percentage in seeds. This study comprised some Egyptian cotton cultivars ie., Giza 80, Giza 83, Giza 90 and Giza 91 (belong to Upper Egypt cultivars) and Giza 45, Giza 70, Giza 85 Giza 88, Giza 86 and Giza 89 (belong to Lower Egypt cultivars) during 2005 and 2006 seasons. Plants were irrigated with saline solution of NaCl at concentrations of 4000, 8000 and 12000 ppm. After 50 days from sowing alternately with tap water up to the end of the growing season. The control plants were irrigated regularly with tap water during the whole season. The results obtained could be summarized as follows: Cultivars responded differently to irrigation with saline water. Salinity tended to reduce leaf area and dry weight of stem, roots and leaves. In addition, salinity decreased number of flowers / plant, number of bolls / plant, boll weight, seed index and seed cotton yield per plant in grams. Salinity tended to decrease total soluble sugars and reducing sugars in leaves. On contrary, salinity caused an increase in chloroplast pigments and proline. Salinity caused decrease in oil and protein percentage of cotton\ seeds. The most pronounced increase of chemical constituents was observed in proline content in leaves as a result of water stress caused by (salinity). Giza 80 and Giza 45 had the highest values contents of proline under all salinity concentration, the highest values of proline content in their stressed leaves lead to an increase in their yields and its components under saline conditions. For the plant breeder, it is useful to select plants with higher proline contents in leaves to obtain plants more tolerant to salinity.