Se72 has been observed to decay by electron capture with a half-life of 8.40+/-0.08 days, predominantly to an excited state in As72 at 46.0+/-0.3 kev. The half-life of this state is less than 1.5×10-8 sec. Less than 7% of the Se72 decays are to the ground state. The K-conversion coefficient of the 46-kev gamma was measured to be 0.63+/-0.06 and the KL conversion ratio to be 9.7+/-0.5. The upper limit, 0.1%, obtained for the abundance of positrons places a maximum value on the decay energy of 1.2 Mev, which corresponds to a maximum ft of 5.7. On these grounds the excited state is assigned a 1+ spin and the gamma transition is E1. In the course of these measurements, the ratio of intensities of x-rays to 46-kev gamma rays in the decay of RaD (Pb210) was redetermined to be 5.38+/-0.50.