This study will be done with naturally occurring nasal carcinomas in dogs. The purpose is to evaluate the radiation response of tumor and acute and late responding normal tissues to nonconventional fractionation schemes. It has been proposed that accelerated fractionation of the radiation therapy dose might be more effective for control of rapidly proliferating tumors. It has also been proposed that some reduction in late normal tissue complications could be achieved with smaller doses per fraction. If the intertreatment interval between fractions and the overall time to give a total dose of radiation can be reduced, tumors would have less opportunity for repopulation and regrowth. If the dose response curves of target cells for acute and late responding normal tissues are significantly different, late responding normal tissues may be spared by smaller doses per fraction while acutely responding tissues will not experience a corresponding decrease in injury. Tumors are considered to be acutely responding tissues. The research proposed is designed to test the theory and to give estimates of the general shapes of dose response curves for tumor and acute and late responding tissues. Variable total doses will be given to three groups of dogs with nasal carcinomas. Each group will receive a different size of dose per fraction to achieve the variable total doses. All irradiation doses will be given in an interval of four weeks. Analysis will be done to determine the 50% probability for tumor control at one year; the probability for levels of response of acutely responding tissues, particularly the structures of the eye; and probability for late necrosis. The data will permit evaluation of the effect of size of dose per fraction on total dose required for tumor control, early effects and late complications. Isoeffect curves will be constructed for the various tissues using data obtained from each of the three different dose per fraction groups.