Evidence-based Clinical Guidelines (CGs) for Good Clinical Practice (GCP) have emerged to synthesize and systematize a wealth of knowledge from scientific journals that health professionals have been unable to follow. Today, the COVID 19 pandemic requires them more than ever. CGs are defined as a set of systematized claims, based on a systematic analysis of scientific evidence, that point to the performance of GCP; contain an assessment of the usefulness and harmfulness of various diagnostic and therapeutic options. "The Good": CG is necessary for health professionals, patients and society, because the knowledge gained in studies is insufficient to perform GCP in further practice. "The Bad": The shortcomings of the CG stem from; (a) there are still many unknowns in medicine, as funding for scientific research is inadequate; (b) the disunity of different institutions that make recommendations at the global, even local level results in different guidelines, although they are based on identical scientific papers as evidence; (c) most clinical scientific studies exclude groups of patients that make up a significant population in everyday practice and the guidelines more or less (do not) apply to them; (d) the impossibility of implementing the CG, because they are not backed by state regulatory bodies and / or the economy cannot follow them. "The Ugly": (a) the ambition of a large number of practitioners and researchers to be among the authors of the guidelines, although many do not have competence for the subject matter; (b) industry (equipment, drugs, supplements) most often funds scientific research and the interdependence of industry and the "dependence" of the authors of guidelines is often intertwined; and (c) publishing (un) intentionally falsified study results which then serve to "support" some guidelines. often in (un) intentional alliance with the editors of the world's elite medical journals.