Mechanical properties of nitrogen austenitic steels are discussed based on the nitrogen effect on the electronic structure of the γ iron. It is shown that alloying with nitrogen increases the concentration of free electrons, whereas carbon contributes its electrons to the 3d band of iron. A correlation between the electronic structure and stacking fault energy and that between a type of the interatomic interaction (metallic, covalent) and short range atomic order are considered and their role in the nitrogen-caused strengthening of austenitic steels is discussed.