A field experiment was conducted to study the impact of moisture stress at different growth phases in maize using Water Requirement Satisfaction Index (WRSI) during kharif 2004 at Agricultural Research Institute (ARI) farm, ANGRAU, Rajendranagar. The experiment was laid out in RBD (Factorial) with four dates of sowing starting from onset of monsoon at 15 days interval and four “irrigation schedules” viz. irrigation as per water requirement, skipping of irrigation at vegetative, flowering stages and rainfed.. Reduced yields were recorded when irrigation was withdrawn during reproductive phase. A significant positive correlation between WRSI and yield was observed (r = 0.79). Higher WUE was observed with skipping of irrigation at vegetative stage and in rainfed treatments.