ABSTEACTTwo field experiments were carried out in El-Gemmeiza Agricultural Research Station Agricultural Research Center, El-Gharbiya Governorate in 2016 and 2017 seasons to study the effect of foliar application with bentonite (times of application and rates) on leaf chemical composition, plant growth, earliness traits, fiber quality and yield of Egyptian cotton (Gossypium barbadense L.), Giza 86 cultivar. A split-plot design with three replicates was used. The main plots included three intervals at (squaring stage and flowering initiation), at (flowering initiation and the top of flowering) and at (squaring stage, flowering initiation and the top of flowering). The sub plots involved four rates of bentonite; (control "without application", spraying with 2, 3 and 4 kg bentonite/fed). The important results could be summarized as follow: Times of foliar application with bentonite gave significant effect on nitrogen, potassium, phosphorus, chlorophyll (a), (b), total chlorophyll and carotenoids concentrations in cotton leaves, in favor of foliar application with bentonite three times (at squaring stage, at flowering initiation and at the top of flowering). Leaves concentrations of nitrogen, potassium, phosphorus, chlorophyll (a), (b), total chlorophyll and carotenoids significantly increased with foliar application of 3kg bentonite /fed as compared with the other rates.The interaction between times of bentonite as foliar spraying and its rates had significant effect on chlorophyll (a), (b), total chlorophyll and carotenoids concentrations in cotton leaves, where foliar spraying with 3kg bentonite per fed three times (at squaring stage, at flowering initiation and at the top of flowering) produced the highest values of these traits. While, leaves N, P and K concentrations did not affect by this interaction. Times of application did not affect plant height and number of fruiting branches/ plant at harvest in both seasons. Bentonite at the rate of 2kg/fed significantly increased cotton growth parameters, i.e., plant height and number of fruiting branches/ plant at harvest as compared with the high rate of betonies(4kg/fed) in both seasons. The interaction significantly affected these two traits in the first season only, where the highest values of cotton growth parameters, i.e., plant height and number of fruiting branches/ plant were, generally, recorded with foliar application of bentonite at the rate of 2kg/fed three times(at squaring stage, at flowering initiation and at the top of flowering). However, the lowest values were recorded with foliar application of bentonite at the rate of 4kg/fed three times (at squaring stage, at flowering initiation and at the top of flowering).Times of foliar application with bentonite gave insignificant effect on earliness traits (numbers of total flowers and total bolls / plant, boll setting % and boll shedding %) in both seasons.Bentonite at the rate of 2kg/fed and at the rate of 3kg/fed significantly increased earliness traits (numbers of total flowers and total bolls / plant a...