An experimental was carried out during the year of 1985, at the Federal University of Viçosa, MG, for the purpose of identifying the effects of 2 sites and 4 periods on onion seed storage, in a factorial randomized complete block design. The evaluated periods were: 0, 60, 120 and 180 days, and storage conditions: cool room with controled temperature at 5°C and 75 to 80% relative humidity, and laboratory room conditions. The results showed that seed vigour became altered when the seeds were stored at laboratory conditions, although the germination was mantained good during the six months period of storage. On the other hand, seed vigour and germination were not altered during the test period.