A magnetic spectrometer for the measurement of beta‐ and gamma‐ray energies has been constructed. By using an inhomogeneous field varying radially in the proper manner, it is possible to bring electrons which leave the source with an extremely wide spread in angle to essentially a perfect focus in 180°. It has thus been possible to use a large mean radius of curvature of 40 cm in order to obtain high resolution combined with a reasonable transmission of about 0.1 percent of the total solid angle. Under operating conditions, with a 0.4‐cm wide source, the full width at half maximum for an internal conversion line is 0.5 percent. Scattering and background effects are negligible.