This paper extends the study of resonance rectification phenomena in plasmas to the case where a static magnetic field is present. Parallel wire‐probe geometry has been chosen so that the rf electric field is primarily perpendicular to the magnetic field. Under these conditions, experiments show that there are two distinct series of resonance peaks, one occurring between successive cyclotron harmonics, the other precisely at the cyclotron harmonics. Cold‐plasma theory is inadequate to account for the existence of these resonances. An explanation is proposed, based on the form of the warm‐plasma permittivity component perpendicular to the magnetic field, which explains satisfactorily all of the experimental observations.