Two field experiments were carried out on squash CV.Eskandrani in the two summer seasons 2005 and 2006 to study the effect of Atonik seed treatments at 0, 25 and 0, 5 ml / L or foliar spray treatments 0, 25 and 0, 5 ml / L and their combination on vegetative growth, sex expression and yield of squash plants. The obtained results are summarized as follow:- 1- Atonik treatments (seed soaking or foliar spray) caused a significant increase in vegetative growth characters, expressed as number of leaves, plant height, and plant fresh and dry weight over control. 2- Atonik treatments over rise to  a significant decrease of male flowers and caused a significant increase in female flowers and reduced sex ratio in both seasons.     3- Atonik treatments inducted a significant increase of yield of squash (No. of fruit / plant, average fruit weight, number of fruits / plant, yield Kg per plant and yield ton / fed. ) compared with control . 4-Seed soaking 0.5 ml / L plus foliar spray 0.5 m / L gave higher values over than the other treatments. Finally, it can be concluded that the best treatment is soaking of squash seeds combined with foliar sprays of Atonik at 0.5 ml / L for  improving  the yield.