The perturbative method for calculating the effect of imperfectly conducting walls on the propagation of electromagnetic waves in cylindrical waveguides is reformulated. The equation for calculating the corrected eigenvalues is obtained in a quite different form. In comparison with the previous result

it is physically more transparent

formally simpler and more compact

and more convenient for practical calculations. 〖JP2〗Special cases overlooked previously are discussed. Results on the coaxial line are presented.〖JP〗