A new particle simulation model has been developed to investigate Cˇerenkov masers. The novel aspects of the code are briefly described, and results of simulations of two types of Cˇerenkov masers are presented. The first device uses a conventional dielectric lining as its slow‐wave structure. The second is a new type of Cˇerenkov maser in which a circular waveguide is partially filled with a dense annular plasma instead of a dielectric layer. Both simulations agree well with experimental results and linear theory calculations. Saturation of the instability is shown to be due to trapping of the beam electrons. The relative merits of each system are discussed.