Elemental Ti, Cr, Zr, Nb, Mo and Ta powders were milled in vibrational ball mill under nitrogen atmosphere. The absorption of nitrogen atoms by powders during milling was followed by measuring the pressure reduction in nitrogen atmosphere. It was found that all the powders absorbed about 50 at.% of nitrogen atoms during milling, resulting in the formation of nitrides having NaCl-type structure. The absorption rate of nitrogen increased with increase in the chemical affinity of the powder elements with nitrogen, i.e., it increased in the following order: Cr, Mo, Ta, Nb, Ti and Zr. The kinetics of nitriding of Ti and Nb powders by MA was analyzed by milling with several different frequencies of vibration, f. The absorption rate of nitrogen was approximately proportional to f³. This fact implies that the nitrogen absorption occurs at the instance of ball collision, and the quantity of nitrogen absorbed at one collision event is proportional to the mechanical energy supplied to the powder.