The desirability of having large sound single crystals of EuO for a number of physical measurements has been well established. Although crystals of EuO had previously been grown, they were either of poor quality, primarily because of container contamination, or too small for many measurements. We report here on a method of growing large, single-phase, mechanically sound crystals of EuO. The method is one where growth takes place from a solution containing an excess of europium metal. The solution, sealed in molybdenum crucibles, is cooled from 1950°-2000°C at the rate of about 25°/h. Centimeter-size crystals were grown and shown to be of extremely good quality by an examination of their Laue spots and their microstructure. The crystals have a lattice constant of 5.1451 Å±0.0003 and a density of 8.180±0.002. The data from the crystal-growing experiments were used to propose a phase diagram in which EuO, when pure, is shown to be an incongruently melting compound. © 1966 The American Institute of Physics.