The theory of finance is based on the assumption that markets work perfectly; But it is known that the markets are far from perfection because in reality the parties can not reach the same information in the same time frame. The optimal level of information symmetry varies depending on different environments and business circle. Among the traders in the market there is an asymmetry in terms of level of knowledge and this asymmetry is sometimes going to disrupt the market operation. In markets where asymmetric knowledge is intense, it is getting more and more away from perfect competition conditions. The elements that disrupt competition disrupt market balances and cause many economic problems. In recent years mortgage problems, especially observed in US markets, have been a result of the adverse selection problem and reiterated its importance. The aim of this study is to examine the effects of asymmetric information on the credit market in the Turkish banking sector. Because of the asymmetric information, adverse selection and moral risk in the banking sector, we have examined the concepts of adverse selection and moral hazard in our study. In particular, credit market indicators such as total loans and non performing loans have been examined and market valuation has been made. In order to determine the credit rationing , the ratio of the following loans to total loans and the ratio of total loans to total assets for the quarter of 2003:Q1-2017:Q2 period is taken as variable. The relationship between the variables was tested by the Granger causality test. As a result of the findings, no causality relation was observed between the variables and it was determined that credit rationing was not made in the mentioned period in the Turkish banking sector.