Two pot experiments were conducted at the Experimental Station and in the Laboratory of Vegetable and Floriculture Department, Faculty of Agriculture, Mansoura University during the two successive seasons of 2005/2006 and 2006/2007 to study the effect of GA₃ and ABA at different concentrations on vegetative growth, yield and chemical composition of khella plants growing under different potassium fertilization rates. The obtained results exhibited that  khella plant height, shoot dry weight and content of photosynthetic pigments in the leaves as well as N, P and K concentrations in the shoots were increased with increasing potassium fertilization levels and the highest values were recorded when the plants received the high level of potassium (45 kg/fed.). GA₃ and its interactions with potassium fertilization increased significantly the plant height, shoot dry weight and N, P and K concentrations in the shoots, while the content of photosynthetic pigments in the leaves was decreased. On the other hand, ABA and its interactions with potassium caused a decrease in the previous parameters except for the content of photosynthetic pigments in the leaves which was increased. Regarding number of umbels and fruit yield per plant as well as the content of khellin and visnagin (%), data showed that potassium fertilization and ABA as well as their interactions significantly increased these parameters. However, GA₃ application alone caused a decrease in number of umbels and fruit yield per plant as well as the principle constituents (%). Meantime, GA₃ with potassium fertilization at  either 30 or 45 kg/fed. increased the fruits content of visnagin.