AbstractThe report presents the results of development of the 170 GHz/1 MW gyrotrons in Russia. The main problems of powerful gyrotrons at present (formation of a high quality helical electron beam, selection of a high efficiency cavity mode, decreasing of inner converter losses, reliable collector and output window) are discussed. The design versions of the main parts of gyrotrons including the short-pulse prototype, first and second versions of industrial models and test set-up are presented. Advanced 170 GHz ITER gyrotrons were also investigated including a single-stage depressed collector versions (CPD) as well as an improved window (CVD diamond window from FZK). The possibility to make high efficient 170 GHz/1 MW gyrotron for ITER is proved by calculations and experiments.