The infrared spectra of protiated and deuterated lead(II) saccharinate monohydrate, Pb(C7H4NO3S)2·H2O were studied in the OH, OD, CO and SO2stretching regions. The spectral characteristics of the HOH and HOD stretching fundamentals were correlated with the structural data on the geometry of the water molecules. Also correlated were the appearance of the spectrum in the CO stretching region, on the one hand, and the number of non-equivalent carbonyl groups in the structure, on the other. An attempt was made to assign the bands which are mainly due to the antisymmetric and the symmetric SO2stretching vibrations.