The stability of ascorbic acid (AA) of irradiated onion bulbs stored at 4 and 20 oC was studied. Gamma ionisation at 0.10; 0.15 and 0.30 kGy causes losses of 10, 13 and 20% of AA content, respectively, and the D value (Decimal Reduction Dose) of AA ionising treatment was estimated at 3.19. During the first 12 weeks of storage AA content decreased in nonirradiated and irradiated bulbs at 0.10, 0.15 and 0.30 kGy, respectively, to 4.52, 4.56, 4.81 and 5.18 mg 100 g-1 FW at 20 °C. At 4 °C, AA decreases to 5.92, 6.53, 6.08 and 5.92 mg 100 g-1 FW. From 12 weeks to the end of the storage period (24 weeks), AA increased but the final concentrations observed were lower than the initial levels and ranged from 15 to 30% less at 20 °C, and from 5 to 20% at 4 °C.