[en] The use of radiotherapy implies the necessity of rigorous quality standards in its different components, aimed to provide the best possible treatment and avoid potential patients' risks, that could even cause him death. Projects of technical cooperation developed in Cuba and supported by the International Atomic Energy Agency address the implementation of Programs of Quality Assurance (PGC) in radiotherapy services. The establishment of the National Quality Audit Program (PNAC) is a superior stage. The National Control Center for Medical Devices, as the national regulator entity for the control and supervision of medical devices in the National Health System, is responsible for the making and execution of the PNAC. The audit modality selected was the inspection visit in situ due to its intrinsic advantages, our geographical extension and the number of radiotherapy services. This paper presents the methodology for the execution of the PNAC, in form of a Normalized Procedure of Operation (PNO) that defines the objectives, scope, terms and definitions, responsibilities, composition and selection of the auditor team, security's conditions, materials and equipment, steps of the audit execution, results calculation and interpretation, records, etc. (author)