Single crystals of rare‐earth arsenate compounds (of the type RAsO4) were synthesized and grown by the flux technique, using lead pyroarsenate as the solvent. Rare‐earth oxides in concentrations of 2 mole % were dissolved in molten lead pyroarsenate (Pb2As2O7) at 1300°C. After 6 hr at temperature the solution was cooled at a rate of 4°C/hr or less for recrystallization of RAsO4. Nucleation and growth occur from 1300° to 925°C. Details for preparation of Pb2As2O7are given. Experiments on the growth of mixed rare‐earth orthoarsenates and mixed phosphate‐arsenate compositions are discussed together with the anomalous behavior of cerium and neodymiu