1. The first period of austenite grain growth in steel 12Kh2N4A at 900\dgC (holding for 2 h or longer) is characterized by the formation of very large grains (grade 2\2-3) among fine grains (grade 9\2-10). The large grains are formed by the coalescence of fine grains into a single grain. 2. At higher temperatures there is less difference in the size of the grains and the shapes are more regular. The grains grow due to the coalescence of small groups of fine grains and migration of grain boundaries. With increasing temperature the mechanism of growth resulting from grain boundary migration becomes predominant.