Infrared spectra of water and deuterated water isolated in neon matrices have been recorded between 20 and 5000 cm(-1). The water concentration has been varied between very low concentrations with only monomers present up to concentrations where pentamers and possibly hexamers are present in significant amounts. The concentration dependencies of the observed absorption bands have been used to assign the dimer spectrum. The matrices studied were on the order of 1 mm thick, which has made it simpler to vary concentrations in a manner which discriminates between higher aggregates. It has also made it possible to avoid the baseline problems which appear when the matrices are only slightly thicker than the wavelengths in the far-infrared part of the spectrum.