In this paper, I consider the Turkish Banking Industry, which is dominated by a few large banks. Using a conjectural variation approach, I estimate a structural model to examine the market conduct of the largest banks for the period 1988-2009. Estimation results suggest that the Turkish banks colluded in the loan market during the sample period where the average mark-up is estimated to be in the range of 44% to 86% depending on the empirical specification. This evidence demonstrates a conflict between market concentration and competition in the Turkish banking industry. Thus, regulatory agencies should be cautious against attempts to increase concentration in the banking industry.