The evaluation of interventions in Public Health is a key element through the process of developing health policies, but it is not free of controversy. For doing this purpose it is essential the use of research outcomes, although there are sticking points related to the traditional approach of Evidence Based Medicine, dominated by the randomized clinical trial as the gold standard. Not always it is possible to develop randomized and controlled studies in Public Health (sometimes due to ethical limitations, or because of the technical impossibility for performing the trial or because conceptual incompatibility) and the interventions are mostly multifaceted, therefore, the interpretation of the results is a complex task. In other hand, the usual criteria for research appraisal underestimates systematically the observational studies which, frequently, are the indicated in Public Health scenarios. Nevertheless, a great advance has been implemented with the generation of strategies as TREND (Transparent Reporting of Evaluations with Non randomized Designs), as well as other instruments like STROBE (STrenghtening the Reporting of OBservational studies in Epidemiology) or MOOSE (Meta-analysis Of Observational Studies in Epidemiology). But regardless of the existence of more or less consolidated critical appraisal tools, we all need a solvent and rigorous way of knowing the outcomes of Public Health interventions. This would make more dynamic the review, design or planning phases, and it would contribute to facilitate the decision-making process when a well grounded knowledge be available. In this paper all the methodological process about searching evidence in Public Health interventions is reviewed, as well as the main sources providing this information, in order to facilitate this task to the Public health professionals.