This report contains a summary of a two phase program for the development of an X-band crossed-field amplifier. The program was initiated with a feasibility study and later resulted in the development of a 1 kw X-band tube. The feasibilitty portion of the program was primarily concerned with computer studies leading to the electrical design of the tube. It was determined that the requirements could be met with an injected-beam tube and did not require the addition of a distributed-emission section. During the developmental portion of the program, circular format tubes were built to meet a rigorous specification. In general, these developmental tubes had adequate power output but were limited in gain and bandwidth. They also had a tendency to oscillate because of rf feedback within the tube envelope. It was determined that higher gain and higher bandwidth with stability could be achieved only with linear format tubes.