Two laboratory experiments were conducted at Gemmeiza Agriculture Research Station (Gharbeia Governorate) to study the effect of both storage and methods of storage on viability of onion seed during the period from August 2006 to August 2008. Randomize Complete Blocks Design with three replications was used. The results clearly showed that : 1-   There was a progressive decline in germination percentage with each increase in the storage period. The decline in germination percentage after 12 months was 10.36 % and 21.42 % after 24 months. Seed germination percentage was markedly affected by methods of storage. Utilizing of polyethylene bags under Frigidaire at 5-8 ºC or freezing resulted in higher seed germination percentage. There was a significant interaction effect of period and method of storage. The higher percentage of germination was observed under the treatment of storage period for 4 months in paper bags without and additions under normal room conditions. 2-   Germination rate (days) was markedly affected by storage period, but differences between treatments were not always significant. There are a progressive increase in number of days to complete germination with each increase in storage period. Germination rate was significantly affected by storage method. The fastest rates of germination were observed with storage of onion seed in polyethylene in normal room conditions. 3-   Seedling length was markedly affected by storage period. Storage at 4 and 8 months were associated with highest length of seedlings i.e . 3.85 and 3.84 cm), respectively. Seedling length was markedly affected by storage method. The maximum seed length (3.84 cm) was observed with storage of seed in polyethylene bags without any additions under normal room conditions It can be concluded that storage onion seed for four months in paper bags in normal room conditions followed by burlap bags in normal room conditions gave the best results in germination percentage and other seedling parameters.