This work was carried out to improve the  quality  and  yield  of  Onion  Giza 6cv. that grown by sets . Sets  were grown on September  12 and 16  in 2006/   2007   and   2007/ 2008  seasons ,respectively  .Plants   were  subjected  to irrigation   treatment  intervals.  Results showed  that , increasing  the  period between irrigations led to a significant reduction in percentage of double bulbs. Application  of   irrigation  later  in   the growing  seasons  gave a    simultaneous increase in total yield. Plots that received  4  irrigations , gave  the lowest  weight  loss .