The paper outlines the constructional and electrical features of a 30-MeV synchrotron. Two types of magnet are described, and theirperformances are compared. Details are given of the accelerating chamber, with its evacuating system, and of the electronic equipment required to control and monitor the machine in operation. The general behaviour is discussed with the help of experimental results. These include the effects of misalignment and disturbance in the magnetic field, gas scattering of the electrons, variations in the injection process, and change in the parameters of the r.f. accelerating field.