The object of the study was the grain of winter barley harvested at the beginning of its setting, milk maturity, dough maturity and full grain maturity stages at nitrogen fertilization doses of 0, 60, 120 and 180 kg N^.ha^-1. The experiment was carried out at the Research Station in Wierzchucinek (53^o26’ N; 17^o79’ E) owned by the University of Technology and Life Sciences, Bydgoszcz. The results of the research revealed that the contents of all the tested individual fractions in total protein generally increased during the filling of the winter barley grain. It mostly concerned prolamins, for which the difference in the contents between stage A and stage D was on average 207.7% for three years of the research. A fraction of spare proteins, i.e. prolamins and glutelins, increased significantly (by 15.7%), whereas the content of albumins and globulins decreased in the protein of ripening grain of winter barley (by 18.2%) in all the tested stages of grain growth under the effect of nitrogen fertilization (0-180 kg N·ha^-1). The highest effect of nitrogen doses on the protein fractional composition was observed in the phase of full grain maturity. Quantitative variations in proportions between protein fractions during the ontogenesis of the winter barley grain in relation to the intense nitrogen fertilization may suggest some decline in nutritional value of the protein.

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