Protein changes in roots of winter wheat were investigated on the 3rd and 8th day after a rapid temperature shift-down from 25°C to 4°C. Proteins were labelled during the last 12 hours before harvesting using L-[l4C] aminoacid mixture and were analysed by scintillation counting, one- and two dimensional gel electrophoresis and fluorography. The total uptake of the label was about 10 times lower in the treated plants of both series. A prominent band with molecular mass of 43±3 kDa and an isoelectric point between pH 6.8–7.4 was observed on the 3rd day after treatment. The obtained results suggest a transient expression of the 43 kDa protein (s) and may be an indication for its involvement in the development of the cold stress response.