The variations of glucose, fructose and sucrose in onion bulbs irradiated at 0.15 and 0.30 kGy and stored at 4, 10 and 20°C were investigated. Between 5 and 8 weeks glucose increased in concentration and varied between 3 and 3.7 g×100 g�1 of fresh weight at these temperatures. The same pattern was observed in the fructose, however, the increase varied between 1.4 and 2.93 g×100 g�1 of fresh weight. During the last 15 weeks of storage, the glucose and fructose remained stable, ranging between 1 and 1.5 g×100 g�1 of fresh weight. The fructose/glucose ratio was slightly higher in the control bulbs, but in the ionised bulbs, the ratio remained relatively constant. However, the sucrose content remained constant except for a small increase observed after six weeks and was between 0.61 and 1.09 g×100 g�1 for the control and 0.30 kGy for the treated bulbs respectively at 10°C, and 0.73, 1.23 and 1.16 g�1 ×100 g for the control, 0.15 and 0.30 kGy for the treated bulbs at 20°C, respectively.