Harvesting date and storage period has considerable influence on wheat seed quality as measured by germination ability under favorable and stress conditions and seedling vigor as well. Tow field experiments were conducted at Tag El-Eiz Experiment Station, AgricultureResearchCenter during2005/2006 and 2006/2007 seasons, while storage studies and viability tests were conducted at Giza seed Technology Lab. under common conditions from June 2006 till December 2008. The aim of this study was to investigate the effect of three harvesting dates i.e, 60, 70 and 80 days after 50% heading and four storage periods i. e. 0, 6, 12 and 18 months on wheat seed quality. The results revealed that early harvesting (60 days after 50% heading) reduced seed germinablity under optimal and stress conditions, seedling vigor and seed electrical conductivity. Meanwhile, seed harvested after 70 and 80 days after 50% heading had high viability so that the differences in quality measurements were insignificant. The results revealed also that prolonging storage periods cause deterioration in seed quality and it was more obvious in earlier harvested seeds and those had high moisture content. Moreover, the variation in seed moisture content at harvesting time and during storage was related with the degree of seed deterioration. A combination of quality traits or lab. Testes are more useful than evaluation of one trait by single test. The results suggested harvesting wheat seeds (c.v. Giza 168) after 70 days from mentoring 50% heading or with about 14 % moisture content and storage for 12 month under open-air storage in order to have seed germination above the standard of wheat certified seed (85%).