Stereotactic radiosurgery (SRS) is a precise focusing of radiation to a targeted point or larger area of tissue. With advances in technology, the radiobiological understanding of this modality has trailed behind. Although found effective in both short- and long-term follow-up, there are ongoing evolution and controversial topics such as dosing pattern, dose per fraction in hypo-fractionnated regimens, inter-fraction interval, and so on. Radiobiology of radiosurgery is not a mere extension of conventional fractionation radiotherapy, but it demands further evaluation of the dose calculation on the linear linear-quadratic model, which has also its limits, biologically effective dose, and radiosensitivity of the normal and target tissue. Further research is undergoing to understand this somewhat controversial topic of radiosurgery better.