Abstract. Gamma-gamma coincidences and singles measurements with Ge detectors have been made on transitions in 239Np and 239pu. Eighteen transitions in 239pu and three in 239Np have been verified by coincidence data. High resolution singles measurements were made and new values for the energy and intensities of'/-rays below 350 keV were obtained. IntroductionThe nuclide 243Am decays by alpha-particle emission to 2.35d 239Np which proceeds by fl-decay to 239pu, the levels of which have been established by c~-7 and e--7 coincidence studies [1][2][3][4][5][6][7], as well as by singlenucleon transfer reactions. However, only a few of the gamma transitions have been confirmed by coincidence data. The level structure of 239Np from 243Am decay was studied by Engelkemeir [8,9] by c~-7 coincidences and conversion electron spectrometry. However, since 243Am decays preferentially to the low lying energy states, no 77 coincidence measurements had been attempted. Therefore, it is the purpose of this study to confirm by coincidence measurements the previously placed 7-ray transitions in 239Np and 239pu, as well as to perform a thorough reexamination of these nuclei following radiochemical purification of the sources. Both singles and coincidence 7-ray spectroscopic techniques were employed with the exclusive use of high resolution Ge detectors.