We investigate the effect of neutrino Comptonization, by which energy is exchanged between a hot, dense nucleon gas and a neutrino gas via Compton scattering, on the final spectrum of the neutrinos. We derive the diffusion equation which governs Comptonization, and integrate it to get energy exchange rates. We use the rates and other reasonable assumptions to develop rough criteria by which it is possible to determine whether or not Comptonization will be important in a gas of given temperature and density. We construct a crude model transport equation which accounts for several of the processes that cause energy exchange between neutrinos and the gas and calculate spectra. We conclude that Comptonization can have a marked effect on neutrino spectra whenever our rough criteria are satisfied. When applied to conditions likely to occur during stellar core collapse, we find that COmptonization will be important for densities in excess of 10/sup 13/ g cm/sup -3/ and temperatures in a wide range about 10/sup 11/ K in a free nucleon gas. A dominance of high-A nuclei, however, will make Comptonization less important than electron scattering, typicallly, due to the larger number of electrons per baryon Y/sub e/ necessary to cancel the chargemore » of the protons found in the nuclei.« less