[In search of the best evidence].

Evidence-based practice is an approach involving the definition of a problem, the search for and critical evaluation of available evidence, the implementation of evidence in practice and the evaluation of the results obtained. In order to implement this approach in nursing, nurses must know how to obtain, interpret and integrate evidence stemming from research in the care rendered to patients and their relatives. Based on the literature, this article presents theoretical considerations concerning the hierarchy of evidence and where to search for the best evidence.