Raman and i.r. spectra of vitreous sodium oligophosphates $xNa_{2}O \cdot P_{2}O_{5}$, with x between 1,000 and 1,625 are reported and discussed. As x increases, gradual modifications are particularly observed in the Raman spectra by the weakening of some typical bands of the glass with x = 1,000—Graham salt-—and the appearance of new bands. In the spectra of the glass with x = 1,625 these bands are discussed in relation to the Raman spectra of melted polyphosphates with low molecular weight.