Abstract A free electron laser driven by an induction linac has been investigated by experiments and theory. Preliminary experimental results for a 6 MeV, 1 kA induction linac FEL are presented. In the experiment, a distributed feedback resonator is introduced to obtain a narrow spectrum. As a result, a typical double peak spectrum for a distributed feedback laser was observed. For planning future experiments, 3-dimensional simulations have been performed on the FEL energy conversion efficiency for multitransverse mode excitation. The wiggler tapering is found to be effective only for the single mode excitation, but not for the multimode excitation.