Gamma radiation doses of 3200, 4700, 6500, 7900 and 9500 rad completely inhibited sprouting of Brigham Yellow Globe onions in a 300-day test period during which 75 per cent of the non-irradiated controls sprouted. In a second test of equal duration, using controlled temperature storage and shed storage, less than 3 per cent of Autumn Spice onions exposed to either 4000 or 8000 rad sprouted, whereas more than 79 per cent of the non-irradiated bulbs sprouted. Irradiation reduced sprouting of Yellow Sweet Spanish onions in both tests.Some evidence indicated that the smaller bulbs in both the irradiated and non-irradiated lots were less susceptible to storage rot. In Brigham Yellow Globe, the incidence of internal discoloration of the growing point was greatest with the highest radiation dose. Irradiated onions were milder in flavour.