The effects of low temperatures on the break of dormancy of onion bulbs and changes in oligosaccharides, phenolics and peroxidase activity were examined. Cold treatment at 9°C was more effective on break of dormancy than at 0°C, but in both cases cold temperatures caused a rapid break of dormancy. Changes in oligosaccharides and glucose were linked to sprouting stages, with higher concentrations at the onset of sprouting for cold treatments of 9°C for 3 weeks and 0°C for 2 weeks; for the other treatments (9°C for 2 weeks and 0°C for 3 weeks) the high concentrations were reached after sprouting. There was an inverse relation between sprouting on the one hand, and phenolics and peroxidase activity on the other hand. These results emphasized a positive effect of low temperature on breaking dormancy of onion bulbs and the negative role of phenolics and peroxidase on inner bud development.