This work aims to provide a thorough summary of the main theoretical frameworks for the study of credit rationing. This subject was approached from several theoretical points of view and in the second part of the 20th century many models have been developed. After a first treatment in the context of the availability doctrine, the concept was more deeply defined in the so-called “à la Hodgman” models. Later, Stiglitz and Weiss (1981) developed what is widely recognized to be the canonical framework for credit rationing. From then on, many economists studied the issue from different angles, incorporating elements like the reputation of the firm, the role of collateral, the presence of monitoring and the existence of self-rationing.