Accelerated aging test results were found to be affected by many factors namely;  relative humidity, temperature degrees, exposure periods and seed chemical composition. Therefore, precaution should be taken when utilizing this test for evaluating seed viability. This study was carried out at Seed Technology unit, Mansoura, Dakhlia Governorate during 2010 and 2011 years, to determine the value of accelerated aging test conditions for evaluating seed vigour and its relationship to chemical composition of  the tested seeds (wheat, soybean and sunflower). The main results could be summarized as follows: Conducting the accelerated aging test at the highest  surrounded relative humidity level (100%) led to increasing seed moisture content and the increase was more rapidly comparing to conducting the test with using saturated salt solutions (SSAA)  such as sodium hydroxide (75%Rh.). Increasing temperature degrees during the aging test release seed water absorption specially at saturated relative humidity (100%). Seed moisture contents increased  as the exposure  period to accelerated aging conditions was  increased. Also soybean seed was more sensitive to the accelerated aging conditions especially relative humidity comparing to sunflower and wheat seed. So, the results suggest conducting the accelerated aging test for soybean seed at relative humidity 75% and  temperature degrees not excesses 44C^o for 72hour., (100% relative humidity, 41C⁰  for 72 hour) for wheat and (100% relative humidity, 44C⁰ for 72 hour) for sunflower.