It is well known that a number of medical interventions are still based on personal practitioner impression, non-systematic clinical experience or pathophysiologic rationale rather than solid scientific evidence, even when available. Evidence based medicine consists in systematically finding, appraising and using validated research results as a basis for clinical decision making. Access to evidence is essentially provided by randomized clinical trials. One can hope that medical practice supported by the best available evidence about diagnosis, prognosis and therapy will lead to some improvement in patient care. Nevertheless, the field of grey zones is still so large in clinical practice (where incertainty is mainly the rule) that evidence based medicine remains for the moment a positive mental attitude more than a pragmatic and generalizable approach.