Both the free‐electron laser (FEL) and cyclotron‐maser (CM) instabilities can play a role in wave generation laser experiments employing both an axial guide magnetic field and a transverse wiggler magnetic field. The experimental distinction between these two mechanisms can only be made by comparing measured radiation characteristics with the predictions of either model. For a recent intense beam experiment [Phys. Fluids26, 2683 (1983)], most of the data are in good agreement with the FEL mechanism, as previously concluded, rather than with the CM instability, and the data taken far from gyroresonance are of unambiguous FEL origin.