The results and detailed discussion of an extensive experimental study of infrared spectra of the x(PbO)-(1 - x) P2O5 vitreous system (x = 0.3-0.75) together with a brief review of infrared spectra of phosphate compounds, are presented. Theoretical models employed in the interpretation of infrared spectra of glasses have been reviewed. The frequency ranges of various infrared bands belonging to PO43- and P2O74-, observed in different phosphate compounds, are discussed. The glassy and quenched samples were prepared from PbO and NH4H2PO4 by the rapid quenching technique. The infrared spectra of the constituents of the system, PbO and P2O5, in their polycrystalline and glassy forms, have been discussed. The intensity and wavenumbers of the infrared bands around 1600 and 3300 cm(-1), assigned to the bending and stretching modes in H2O trapped by the hygroscopic glasses, have been followed for different compositions with x < 0.5. The changes observed in these infrared bands established the role of water as an additional glass modifier. The intensity and frequency variations of the infrared bands have been followed th rough all the com positions for characteristic phosphate group frequencies including P=O, P-O-P stretching and bending modes and P-O bending mode. The results clearly suggest that the x(PbO)-(1 - x) P2O5 system undergoes gradual structural changes from metaphosphate (x = 0.5), to pyrophosphate (x = 0.66) and to orthophosphate (x = 0.75). The continuing presence of the infrared band, in varying intensity, in the region 1200-1280 cm(-1) attributed to P=O, suggests that the glass-forming ability of the binary system is extendable at least up to x = 0.66 composition, and that no complete rupture of P=O bond by Pb2+ takes place.