This is a review of the literature about the use of odds ratio, a tool to measure the association between an event and an exposition, which is employed in case-control studies and other statistical analyzes where the limitation to use measures that depend on the incident is present. The odds ratio interpretation is complicated, it can be understood as the ratio between the odds that outcome will occur be given a particular exposure and the odds that outcome will be occurring in the absence of it. Relative risk, like odds ratio, is used to measure an association; however, their interpretation is different. The purpose of this review is to explain the use of the odds ratio in health research, facilitating it’s interpretation and establishing differences with relative risk.