Experiment was conducted in 2008 at Agricultural Research Station, Isfahan University of Technology to evaluate the effects of foliar application of proline and glycine betaine on the response of sunflower to water stress using a randomized complete block design with a split plot layout with three replications. The study included three irrigation regims (irrigation after 70, 100 and 130 mm cumulative pan evaporation) as the main plot and five foliar application treatments in 20 and 50 mM Proline and 50 and 100 mM Glycine betaine and no foliar application (control) as subplot. Number of days from planting to flowering and physiological maturity, chlorophyll fluorescence parameters (F 0 ، F M و F V /F M ), leaf area index, number of seeds per head, seed weight, oil percentage, plant dry weight, harvest index and water use efficiency was measured. Number of days from planting to flowering and maturity was decreased as the period between irrigations was increased. Under 130 mm irrigation regime the number of leaves per plant, leaf dry weight, leaf area index, number of seeds per head, grain yield, plant dry weight, grain oil percentage and oil yield was significantly less, compared to 70 mm irrigation regime. However, the differences between 70 and 100 mm irrigation regimes were not significant in terms of mentioned parameters here. The effects of irrigation regimes were not significant on the chlorophyll fluorescence parameters as well as on plant height, seed weight and harvest index. Water use efficiency was higher at 100 and 130 compared to 70 mm irrigation regime. Foliar application of proline and glycine betaine to some extent shortened the period between planting to flowering and physiological maturity. Foliar application of 20 mM proline was significant positive effect on chlorophyll fluorescence parameter of F V /F M , plant height, number of seeds per head, grain yield, oil yield and water use efficiency whe compared to non- foliar application treatment (control). The effects of foliar application of proline and glycine betaine were not significant on the number of leaves per plant, leaf dry weight, leaf area index, plant dry weight and grain oil percentage. In general, the 100 mm irrigation regime compared to the two other irrigation regimes was superior in terms of having higher values for grain yield, oil yield, harvest index and water use efficiency. The results from this experiment showed that foliar application of proline and glycine betaine especially 20 mM Proline may improve the yield and the water use efficiency of sunflower plants. Key WordS: Foliar application, Proline, Glycine betaine, Water Stress and Sunflower.