The disintegration of RaB was studied by a β-ray spectrometer, with coincidence counter techniques. The β-ray spectrum of RaB obtained was complex, consisting of two components with end point energies 590±10 and 650±10 Kev. This results was also confirmed by coincidence measurements between the internal conversion electrons of the 242, 295 and 350 Kev γ-rays of RaC and the β-rays of RaB, using a pair of 180° focussing spectrometers. The relative intensities of the two β-ray groups obtained 5:4 was in accord with the excitation probabilities given by Ellis, and also with the transition probabilities calculated from the γ-ray intensities obtained by Muller et al. Judging from these experimental results, the level scheme proposed by Ellis seems to be more plausible than that of Stern.