The growing array of diagnostic and therapeutic options available to the clinician has created the necessity of techniques, such as the randomized clinical trial, to evaluate their effectiveness. Recently, with the increasing penetration of the methods of clinical epidemiology into medical practice, the concept of an evidence-based medicine has arisen. Emphasizing the necessity of solid clinical evidence for clinical decision-making, evidence-based medicine provides a framework for the integration of research results into clinical practice. The evidence is graded, principally on the basis of study design, and norms are established as to what constitutes adequate evidence for clinical decision-making. The combination of this new paradigm of medical practice with the power of modern telecommunications is causing a revolution in the way medicine is practiced. Its integration into clinical practice is being facilitated by quantitative overviews of the literature, and the creation of clinical guidelines based on these reviews. Shortcomings of the traditional sources of evidence have been documented. New sources of evidence, such as the ACP Journal Club, and the Cochrane Collaboration, diminish dramatically the time required of clinicians to obtain the best available evidence. All health professionals should familiarize themselves with evidence-based medicine.