Stereotactic radiosurgery is a highly conformal form of radiation therapy that delivers a high dose of radiation in a single treatment. Since stereotactic radiosurgery is commonly used for brain cancer treatment it is critical that the healthy tissue surrounding the tumor receives as little damage as possible This thesis aims to quantify and compare the uncertainty in treatment plan quality in select phases of the treatment process for metastatic brain tumors treated with stereotactic radiosurgery. While uncertainty is unavoidable in radiation therapy, stereotactic radiosurgery treatment requires strict quality assurance measures to minimize its effect. In order to quantify uncertainty, metrics specifically developed for stereotactic radiosurgery were used to evaluate plan quality. Three important steps in the radiosurgery process were investigated. The first step was contouring or tumor delineation in which the effect of inter-observer contouring variation on plan quality was quantified. The second step was treatment planning in which uncertainty in plan quality due to the effect of calculating plans with different treatment planning algorithms was quantified. The third step was treatment delivery in which plan quality variation for a simple model was quantified for geometric misalignments. Overall a high degree of variation was found to be introduced into the process during the contouring phase as this phase is inherently subjective. Plan quality is directly linked to patient outcome and an understanding and quantification of the uncertainty will improve patient treatment.