The present work was carried out on the Experimental Farm, Faculty of Agriculture, AssiutUniversity, Assiut during 2005/2006 and 2006/2007 seasons to study the effects of planting date and dry set size on emergence percentage, final stand and yield and its components of onion cv. Giza 6 grown by sets. Planting on September 15^th gave the highest emergence %, final plant stand and the highest of single center bulbs percentage while early planting at August 15^th exhibited the least % of the two parameters.  Planting at Aug.30^th resulted in the highest single bulbs yield per feddan the lowest percentage of bolting and the highest weight of double bulbs per feddan.  Planting on August 15^th gave the highest percentage of double and bolter bulbs and weight of bolters per feddan.  .Using of 3 cm dry sets resulted in the highest percentage of emergence and final stand, the highest bolting percentage, the highest bolters and single bulbs weight per feddan and the highest total yield per feddan. The interaction (set size x planting date) was significant in many of studied characters.  Planting at Aug.30^th using of 3 cm diameter sets resulted the highest total yield per feddan.