The metrological reliability of electromedical equipment, although essential in order to guarantee the desired effects and to avoid adverse effects, is often not verified after the equipment is sold and being used (post-sale period). This is partially due to the fact that, usually, health-care takers that use the equipment are unaware of the risks involved, in other words, there is a low metrological culture in the healthcare environment. In this dissertation, vulnerable aspects regarding the inadequate use of high frequency surgical equipment, also known as electrosurgical unit (ESU), were identified, and their consequences evaluated. Based on these results, technical and standard parameters important for the metrological reliability of ESUs, were evaluated. This dissertation also includes a detailed bibliographical research of basic principles, technical specifications, and international procedures that guarantee the metrological reliability of electrosurgical units. The scope of national standards was evaluated in order to guarantee the correct use of all of the ESU´s functions and modes. Experimental data for the metrological evaluation of the EUSs were collected in three (3) hospitals, one (1) private and two (2) public. The results are helpful for evaluating their metrological reliability, and indicate that not only that there is a need for a periodical metrological evaluation, but also that other parameters should be included in existing standards. Part of this dissertation was financed by the Convênio referência FINEP n° 22.01.0692.00 of the Programa Tecnologia Industrial Básica e Serviços Tecnológicos para a Inovação e Competitividade MCT/FINEP/FNDCT/Fundo Verde Amarelo, a universitycompany cooperative program.