Abstract: The effects of low temperature and PEG pretreatments on callus formation and IAA oxidation of mature embryos of wheat were investigated. The results showed that the formation of callus from mature embryos of two wheat cultivars was promoted by both the low temperature and PEG pretreatments. The low temperature reduced the activity of IAA oxidase of ‘Zhengyin 1’ but not ‘Bao 7059’, while PEG enhanced the activity of IAA oxidase of ‘Bao 7059’ but not ‘Zhengyin 1’. Both pretreatments decreased the activity of IAA peroxidase.