We have investigated the composition and structure of thin films of PbZrxTi1-xO3 (x-0.54) produced in situ by pulsed excimer laser deposition from a stoichiometric pressed oxide target. Thin films were deposited onto (100) MgO and SrTiO3 substrates as a function of substrate temperature between room temperature and 750 °C, and oxygen background pressures between vacuum and 300 mtorr. The deposited films were very smooth with particulates covering less than 0.5% of the surface. Elastic backscattering spectroscopy was used to determine the relative atomic fractions. In the deposited films, the Pb stoichiometry was found to be very sensitive to both the substrate temperature and the O2 background pressure. Above ∼600 °C, the Pb content dropped rapidly with increasing substrate temperature for a 50 mtorr 02 background. At 550 °C the Pb content was near-stoichiometric for O2 background pressures between 200 and 300 mtorr but dropped monotonically to ∼20% of the expected value for depositions in a vacuum (i.e., no O2 background). Over this entire range of pressures and temperatures the Ti/Zr stoichiometry ratio was relatively uneffected. The structure and orientation of the deposited films, as determined by x-ray diffraction, followed the Pb deficiency via the production of other phases and orientations. Crystallation of the deposited film was observed at temperatures as low as 400 °C for 200 mtorr O2 background. At 550 °C and 200 –300 mtorr, (100) oriented PbZrxTi1-xO3 was observed on SrTiO3 substrates.