Abstract: Greenhouse and field studies were conducted at the University of Jordan Research Station during 2000/2001 growing season to examine the influence of Mepiquat Chloride (1,1-dimethyl piperidinium Chloride) and Ethephon (2-chloroethyl-phosphonic acid) on growth, yield and water use efficiency of two selected wheat cultivars (Namely, Hourani 27 and Petra, Triticum turgidum L. var. Durum). In greenhouse pot experiments, seeds of wheat cultivars were soaked in Mepiquat Chloride solution at a rate of 0, 250, 500 and 750 mg kg-1 in one experiment. Ethephon was sprayed independently at a rate of 0, 150, 300 g ha-1 at the Zadoks 10 and 20, respectively in a second experiment. Plants in both experiments were subjected to two moisture levels: No stress and water stress for the entire growth period of the two cultivars. In field experiments, Ethephon solutions was sprayed independently at a rate of 0, 150, 300 and 450 g ha-1 at the Zadoks 10, 20 and 30, respectively in the first experiment. Seeds of both cultivars were soaked in Mepiquat Chloride solution at a rate of 0, 250, 500, 750 and 1000 mg kg-1 in a second experiment. Mepiquat Chloride and Ethephon treatment had no influence on shoot: root ratio of cultivars. Grain yield of cultivars grown either under well water or water stress conditions increased with Mepiquat Chloride treatment. Ethephon treatment only increased grain yield and harvest index of Hourani cultivar under well-watered conditions in both greenhouse and field experiments. This might be attributed to the increase in the number of fertile tillers per plant.