Linear accelerators are one of the most common machines in the delivery of radiation therapy. Establishing well-known values of accelerator and beam characteristics, includingdepth dose and profile information, is imperative to delivering a planned dose distribution accurately. This process of evaluation and beam characterization is composed of two parts: acceptance testing and commissioning. After this is completed, linacs are regularly evaluatedto establish that the machine is correctly functioning and that it, among other things, is still delivering dose within some tolerance level of the characterization determined during acceptance testing and commissioning. This regular quality assurance (QA) process comprises of different tests and/or levels of rigor depending on several factors including the frequency with which a given test is performed: annually, monthly and daily. More complete information about setup and QA for scanning systems is found in the literature. Equipment for acceptance testing is typically very similar compared to commissioning.