The boundary value problem involved in finding the propagation characteristics of electromagnetic waves in a cylindrical tube containing a coaxial d.c. discharge is solved. Ohm's law is assumed to hold for the alternating current. This assumption has been verified theoretically for the case where the alternating electric field is small compared with the d.c. field. Curves which give the relationship between the complex propagation constant, &ggr;, and the complex dielectric coefficient,Kc′, have been computed for the solution in which the TEM mode of the coaxial line is approached asKc′ becomes infinite.