Continued progress in high energy and nuclear physics demands a new generation of particle accelerators, which in turn requires new high-power, high efficiency rf sources. One of the attractive candidates for this role is the magnicon–microwave amplifier with circular deflection of an electron beam. Magnicons have shown great potential with both high efficiency and high power. A first magnicon to have demonstrated these qualities was built and tested in the 80s in Novosibirsk. A power of 2.6 MW was obtained at 915 MHz with a pulse width of 30 μs and an electronic efficiency of 85%. The latest results in magnicon research, as well as the status of current magnicon projects, are presented in this paper. Examples of both operating magnicons and those under development include decimeter wave (1.3 GHz) amplifiers with a power level up to 10 MW in millisecond pulses; frequency-doublers in the centimeter wave range (7 GHz and 11.4 GHz) at a power of 50–60 MW, and a 40 MW frequency-tripler in the millimeter range (34.3 GHz), with microsecond pulses.