Abstract: The four coefficients A, B,C and D of the correlation of ideal gas heat capacity, Cpo =A+BT + CT2 + DT3, were determined for 435 substances by the method of least squares with a digital computer, on the bases of the recently published Cpo data during the period of 1968 to 1978. The average percent deviation of the calculated Cpo from the experimental value is 0.160. The substances were selected according to their relative importance in fundamental chemical industries. Amongst these, either their heat capacity coefficients have not been published in the literature or their heat capacity coefficients are revised in the present work by using recently available published experimental data.