The aim of the present investigation was to study the growth, yield and yield components of maize (Zea mays L.) single cross 704 under different levels of irrigation, plant density and ethephon levels. There were two field experiments during 2003-4 and 2004-5 growing seasons at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. The experimental design was a randomized complete-blocks with four replicates and the treatments in a split-split plot arrangement. Irrigation levels (low and high) were the main plots, the plant densities (53,333 and 80,000 plants ha-1) in the subplots and ethephon levels (0, 0.56, 0.84 kg ha-1 a.i., applied at the 6-leaf stage) in the sub-subplots. The results showed that the rates of ethephon foliar application could play an important role in the maize growth indices and attributed grain yield components. Application of ethephon was associated with a decrease in LAI, LAID and CGR. Furthermore, ethephon reduced plant and ear height. Increasing application rates of ethephon showed a significant reduction in early season plant height and LAI, LAID. The control plants had lower grain yield than those treated with different ethephon levels. Indeed, this research showed that under conditions of water stress, a maize plant is able to make better use of available water if vegetative growth is restricted early in the season. The results also indicated that yield response of maize to ethephon application would vary with the plant density and available water conditions. Ethephon treatment was found to be more beneficial to the grain yield at higher plant densities and water stress conditions and it is worthy of further investigations.