This paper presents the results obtained on measuring the change of dimension of various nitriding steels by nitriding. After nitriding a steel, containing 0.41 % C, 2.62 % Cr, 0.42 % Mo and 0.28 % V quenched in oil from 950° and tempered at 700°, at 500° for 50 hrs, it has been found that the percentage of dilatation of diameter and length decreased with increasing diameter. The tempering temperature, varied from 500° to 700°C, has no influence on the percentage of dilatation. The percentage of dilatation varies with steel composition and it increases with the elevation of nitriding temperature.