We propose to carry out multiwavelength photometry at 4-200 mu of a complete all-sky sample of ultraluminous IRAS galaxies from the QDOT survey, and to perform spectroscopy with LWS and SWS on a few of the brighter galaxies in the sample. The discovery of ultraluminous infrared galaxies was one of the major results of the IRAS mission. Subsequent study of these galaxies has been hampered by lack of access to most of the infrared waveband. Detailed radiative transfer models for starbursts and AGN contributions to the far infrared continuum are porrly constrained by the IRAS fluxes. In most cases only 60 and 100 mu fluxes were detected by IRAS. Although there is a concensus that interactions and mergers play a major role in generating ultraluminous infrared galaxies, there is major controversy about whether massive starbursts or shrouded quasars are the principal contributors to the emission. Detailed spectral energy distributions over a wide spectral range will be a powerful tool in resolving the controversy. Study of a complete sample is essentail for statistical and quantitative conclusions to be reached. Spectroscopy of a smaple of the brighter galaxies at 4-200 mu will allow us to assess the contribution of line emission to the broad band fluxes, provide diagnostic evidence of the presence of starbursts, and give the contribution of broad features from very small grains or PAHs (and the magnitude of depletion of these features) in a variety of environments. The 10 mu silicate feature and its shape is an especially important constraint on radiative transfer models.