The magnetic properties of divalent europium compounds have engendered considerable interest in recent years.1 The Eu2+ ion with an 8S ground configuration might be expected to exhibit magnetic ordering at low temperatures. The oxide, sulfide, selenide, and telluride all exhibit magnetic ordering. Magnetic susceptibility studies in powder samples indicated EuF2 to be apparently antiferromagnetic at 2°K.1 Interest in EuF2 is enhanced by the fact that it crystallizes in the fluorite structure and is stable toward both hydrolysis and oxidation below ∼500°K. The reported ordering, the structure, and the stability of this material prompted us to attempt single crystal studies of the magnetic properties of this compound. Electron spin resonance at X-band frequencies was employed to detect the possible existence of antiferromagnetic resonance (AFMR) in a variety of single-crystal samples which were prepared under a number of different conditions. To our surprise europium difluoride is nonstoichiometric. At liquid helium temperatures, a number of the samples do show a weak AFMR, but always in the presence of a broad (peak-to-peak linewidth ΔH≃3–4 kOe) paramagnetic resonance. This broad paramagnetic resonance, which is typical for concentrated rare-earth compounds, broadens and remains down to the lowest temperatures investigated (≃1.6°K). In some of the samples, which came the closest to stoichiometry and purity, only the paramagnetic resonance was observed. In the samples exhibiting AFMR, a transition temperature TN=19.5°K is observed. The strength of the AFMR signal was found to be proportional to the number of included crystal impurities. The sample having the largest concentration of included impurities had a mole ratio of impurity to host of the order of 10−5. The impurities are hexagonally shaped platelets with an average size of about 0.5×20×20 μ. They are oriented in the (111) planes of the host lattice. An observed uniaxial anisotropy and a direct dependence of the resonance field with frequency is compatible with the high-frequency mode of an uniaxial antiferromagnet. No demagnetizing factors are observed. An exchange field HE=4.84×104 Oe is calculated by assuming the fluorite structure and an ordering of the second kind. For T≪TN, (2HEHA)½=2510 Oe is determined and thus the anisotropy field HA=65 Oe is calculated. the 〈110〉 directions of the host lattice appear to be the easy directions. These measurements indicate that the magnetically ordered inclusions are due to some form of divalent europium oxyfluoride and that the EuF2 host, independent of the exact composition, is paramagnetic down to 1.6°K. Although a simple uniaxial antiferromagnetic model gives good agreement with the experimental data, the possibility of a canted antiferromagnetic ordering cannot be excluded until magnetic susceptibility measurements are made on the inclusions. The complete text of this investigation is being published elsewhere.2