In order to determine how varieties (Giza 32, Toshky 1, Shandawel 3, Takh 1, 2 and 3) and harvesting dates (100, 120 and 140 days from sowing ; DFS) of sesame affecting seed yield, lost and quality, two field experiments were conducted at Experimental Station Farm, Faculty of Agriculture, Mansoura University, in addition to two laboratory experiments were carried out in Seed Technology Research Unit in Mansoura during summer seasons of 2005 and 2006. The main results of this investigation could be summarized as follows: All yield components, seed yield and its loss as well as seed quality characters under study were significantly affected by the performance of six tested varieties of sesame in both seasons. Giza 32 and Toshky 1 varieties surpassed other studied varieties in all studied characters, except protein percentage in the two seasons. Tested varieties could be descendingly arranged according to their seed yield/fed as follows: Giza 32, Toshky 1, Shandawel 3, Takh 1, 2 and 3. Harvesting dates caused significant differences in all studied characters in both seasons. Delaying harvesting date up to 140 DFS resulted in the highest values of plant height, stem diameter, fruiting zone length, capsule length, number of capsules/plant and number of seeds/capsule as well as seed loss percentage in both seasons. Whereas, intermediate harvesting date (120 DFS) produced the highest values of 1000-seed weight, seed yield/fed and improved all seed quality characters in both seasons. The interaction between varieties and harvesting dates had significant effect on most studied characters in both seasons. Harvesting Toshky 1 or Giza 32 varieties after 140 DFS produced the highest values of most yield component characters and seed loss % in both seasons. While, the best seed yield/fed and seed quality characters resulted from harvesting Giza 32 variety after 120 DFS. It could be concluded that harvesting Giza 32, Toshky 1, Shandaweel 3 and Takh 1 varieties after 120 DFS, and Takh 2 and 3 after 140 DFS could maximize sesame seed productivity and quality under the conditions of Mansoura district.