Summary A mixture of uranium dioxide and boric acid (1:10) was bombarded for one hour with a 20 MeV bremsstrahlung from a linear electron accelerator. After bombardement uranium was chemically separated from fission products. The existence of uranium-237 in the purified uranium, formed by (γ, n) reaction, was proved with the aid of beta and gamma spectrometry, and decay curve measurement. The radiochemical purity of uranium-237 was 99.999% immediately after purification, and the specific activity 0.2 mC/g. It was found possible to prepare 1 mC of uranium-237 from one gram of uranium dioxide in a bombardment of several hours' duration.