The present investigation has been carried out at Giza Agricultural Research Station-ARC in the three winter seasons of 2007/2008, 2008/2009 and 2009/2010. The main objective of this work is to investigate the effect of irrigation water regime on onion production. Combined analysis of the three seasons indicated that the highest values of marketable and total yield (t/fad.) were recorded from the wet treatment. Also, average bulbs weight, bulb diameter, number of growing points/bulb were significantly increased with increasing number of irrigations up to five irrigations. Bulb total soluble solids and bulb dry matter content were significantly increased with decreasing number of irrigations and the highest value was recorded with three irrigations. Sprouting bulb %, rot bulbs % and total weight loss % were significantly higher with five irrigations than three irrigations. Seasonal water consumptive use ranged from 1270 to 1981m3. Irrigation water requirements ranged from 2066 to 2920 m3/fad. It can be noted that the highest values of water consumptive use were found to be from the wet treatment. Water use efficiency values were 5.80, 6.36 and 5.49 kg onion bulbs/m3 for water consumed of dry, medium and wet levels of irrigation, respectively. It can be concluded that application of four irrigations could be recommended for good yield and storability; in addition, the medium irrigations regime (four irrigations) produced the highest values of water use efficiency.