Epidemiology is a medical discipline in which the subject of study is a group of individuals who share some common feature. It is very useful to measure and quantify the level of health in populations; describe diseases; identify determinants of disease; act on the control and prevention of these; and to take action planning and evaluation health. Meanwhile, clinical epidemiology is the application of epidemiological principles and methods to problems in clinical practice; and its purpose is to promote methods of observation and interpretation that lead to valid conclusions. For the socalled father of clinical epidemiology, this is a "Science of art of medicine". Science, because it is based on knowledge, logic and previous experience that has no explanation. And art, because it is based on beliefs, judgments and intuitions without explanation. The aim of this manuscript is to summarize the differences between epidemiology and clinical epidemiology; as well as the following concepts: epidemiological object, method and epidemiological strategy.