X-ray diffraction measurements have been performed at the Synchrotron Radiation Source, Daresbury, UK, in a structural study of the rare-earth metaphosphate glasses , and , whose compositions were determined by electron microprobe analysis. Such rare-earth metaphosphate glasses containing high concentrations of rare-earth ions are of growing interest in fundamental studies of magnetic glasses and in optical communications and laser technologies. The diffraction results prove to be consistent with a network model which is dominated by a phosphate glass skeleton having three-dimensional connectivity, constructed from tetrahedra linked to adjacent tetrahedra via bridging oxygen atoms. Results relating to rare-earth - oxygen correlations are consistent with a sixfold to eightfold coordination of the rare-earth atoms, with distances showing the trends expected from the lanthanide contraction: a reduction of the rare-earth ionic radii with increasing atomic number.