Two field experiments were conducted at El-Gemmeiza Res. Station. GharbiuaGovernorateAgric.Res.Center during the two successive seasons of 2006/2007 and 2007/2008. The objectives of this research was aimed to study the performance of some flax varieties i.e. Sakha 2, Sakha 3, Sakha 4 and Giza 8 under different sowing dates (on 20^th October, 10^th  November, 1^st December) and harvesting dates (after 135, 150 and 165 days) from sowing and their effects on  seed yield and its components. The main findings could be summarized as follows. Early sowing on 20^th October significantly increased seed yield/ plant in the first season. Sowing flax on 10^th November significantly increased seed yield/ faddan as compared with the other sowing dates. Delaying harvesting date to 150 days from sowing significantly increased number of capsules/ plant in the second season and delaying harvesting date to 165 days from sowing significantly increased number of capsules per plant in the first season, 1000 seed weight, seed yield per plant and seed yield per faddan in the both seasons. Sakha 3 and Sakha 4 varieties surpassed the other varieties in number of seeds per capsules in both seasons. Sakha 2 and Giza 8 varieties surpassed the other varieties in the seed yield characters, except number of seeds per cpsules . Giza 8 superior the other varieties bor number of capsules/ plant in the first season, 1000 seed weight , seed yield/ plant and seed yield/ faddan in both seasons. It could be concluded that sown Sakha 2 or Giza 8 early  on 10^th November and harvesting it after 165 days from sowing  maximized seed yield/ fad. under the environmental conditions of Garbiua Governorate.