For a sample set of anatomical structures, existing radiobiologic data and models predict improved clinical results from hypofractionation over standard fractionation for some tissues depending on alpha/beta ratios and other biological factors. Predicted results for specific patients may vary with individual anatomy, and large-scale clinical conclusions can be drawn only after performing similar analysis on an appropriate population of patients. Hypofractionated treatment regimens will be compared with standard fractionation for a number of tumor sites using current radiobiologic models and biologic parameters. The linear-quadratic model and generalized equivalent uniform dose formalism were used to calculate normalized equivalent uniform dose to compare tumor control probability and normal tissue complication probability and complication-free tumor control probability. The robustness of the results was tested for various tumor alpha/beta values and broad interval of biologic parameters such as surviving fraction after a dose of 2 Gy (SF2). At the conclusion of this activity, the learner will be able to do the following: 1. Explain how to apply radiobiological modeling to tumors and normal tissues. 2. Explain the radiobiology differences between conventional and altered fractionation regimes. 3. Compare, mathematically, treatment regimes for different treatment intensities.