This paper explains, at least in part, the problem of information asymmetry, the diffculties that the credit market affected by this problem may encounter and outlines how these problems can be minimized, and in some situations completely eliminated, to improve the quality of the market. Information problems in the credit market, such as negative selection and moral hazard are closely linked to the expected returns on bank loans, which are only partially monotonous functions of the interest rate R. This may be so because too high loan rates can lead to increased default rates that outweigh the rising expected returns that are caused by high loan rates. Thus, the main implication of the existence of asymmetric information is that the loan supply function may be decreasing for high interest rates. If the demand for credit behaves well, that is, as a decreasing function of the interest rate, it may happen that there is no equilibrium of market cleanliness under certain market conditions, i.e. the supply and demand curves do not intersect. This has led to the introduction of an alternative concept of equilibrium, equilibrium credit rationing where demand for credit exceeds supply. Furthermore, the paper also studies the Bester’s model based on heterogeneous clients and the use of collateral as a means of classifying different types of borrowers by the Bank. The Bank offers one contract for each type of borrower and the concept of pooling and separating equilibriums are explained accordingly. The concept of a loan agreement class is introduced and shows that increasing the class eliminates credit rationing.