The nonlinear effects resulting from the propagation of a moderately strong electromagnetic wave in a fully ionized plasma are investigated; a detailed study of the case, when the incident frequency is in the vicinity of the plasma frequency, has been made. The nonlinear contributions to the absorption of the wave and to the reflected components from a plasma‐free space interface, have also been obtained. It is shown, in contrast with earlier work, that under some conditions the nonlinear effects canincreasethe absorption. The generation of harmonic components in the current density and the reflected wave has also been studied.