Nanoparticles of lead sulfide (PbS) have been grown within the pores of polyvinyl alcohol (PVA) matrix on glass substrates by chemical bath deposition at and below room temperature (30 °C). Lead acetate and thiourea, dissolved in an alkaline medium, were taken as the sources of lead and sulfur. X-ray diffraction and selected area electron diffraction studies confirmed the cubic nanocrystalline PbS phase formation. Transmission electron micrograph of the films revealed the particle size lying in the range 10-20 nm. X-ray photoelectron spectroscopic studies confirmed the presence of lead and sulfur in the films, and their atomic ratios were found to be dependent on the deposition temperature. UV-vis spectrophotometric measurement showed a direct allowed band gap lying in the range 2.40-2.81 eV, which is much higher than the bulk value (0.41 eV). The band gap decreases with the increase of deposition temperature. The dielectric constant of the PVA-capped nanocrystalline PbS was in the range 155-265 at higher frequencies, which is much higher compared to only PVA and bulk PbS. © 2008 Elsevier B.V. All rights reserved.