A scintillation gamma‐ray spectrometer has been developed, which is of particular use for the study of isotopes of low specific activity and in which the energies of the gamma‐rays are identified from the pulse height distributions of the recoil electrons produced in an activated NaI crystal. The Compton distributions are easily recognized, and a study of the gamma‐radiation of Co60and I131shows a proportionality to exist between the total light output per scintillation and the energy of the corresponding secondary beta‐ray particle. The noise level of the RCA 5819 photo‐multiplier, as used in this test, corresponded to an energy on the pulse height scale of less than 20 kev. A brief description is given of a new type of differential pulse height analyzer which has been developed for work of this type.