This paper reports the results of a low-temperature NMR experiment on Eu153 in EuO. The data, which are assumed to be linear with magnetization, are compared with calculated values using spin-wave theory. Values of J1kb=0.7500.0025°K and J2kb=-0.09750.004°K are found to give a good description of EuO. This paper also reports the results of NMR studies of the ligands F19 and Cs137 in EuF2 and CsEuF3. These experiments indicate that there is a reversal in sign of the unpaired spin density of the europium ion. The same results are obtained with europium-bearing glasses. This effect is discussed in terms of the Freeman-Watson model of Gd3+ and in terms of a virtual 5d state in Eu2+. © 1966 The American Physical Society.