Until recently, the loan portfolios of savings banks in Korea have tended to concentrate on project financing with higher risks than the conventional loan portfolios of commercial banks. However, these concentrated loan portfolios and other disruptive behaviors led to massive bankruptcies among savings banks in 2011. In the past, many savings banks have experienced a similar bankruptcy process, largely due to the expansion of saving banks' assets through mergers, high risk project financing loan projects, the illegal acts of large shareholders and executives, and the increasing loan concentration of high risk lenders. In particular, the concentration of real estate-related loans became a major management risk factor for savings banks in the 2000s, particularly in the deteriorating operating environment caused by the collapse of the real estate market after the global financial crisis. Furthermore, saving banks' dependence on high-risk loans, such as project finance loans and unsecured personal loans, has intensified in recent years. This is a major factor in the failure of Korean savings banks in the event of external economic shocks. However, due to the limited data collection issue, only a few empirical studies have considered the relationship between the loan concentration ratio of savings banks and bank insolvency. The backdrop to the 2011 insolvency crisis of the savings banks is their large-scale growth and organizational change into a business group, which progressed rapidly up until 2010. Although mergers between savings banks were limited before December 2005, savings banks were already experiencing financial distress at that time due to the household credit crisis in 2003. The number of large savings banks with an asset size of over 1 trillion Korean won increased from 6 in June 2005 to 29 by the end of 2010. As of June 2010, 31 subsidiaries had been opened by 11 savings bank groups. The expansion and integration of these savings banks led to aggressive top-line expansion strategies, including high-risk lending operations and expansions. Over the 2011 to 2017 period, the average total assets of savings banks declined between 2011 and mid-2014 due to the failure of 31 savings banks after 2011, but the assets of the remaining savings banks rapidly increased after 2014. Research on savings bank credit concentration has been limited due to the lack of data, and most recent studies have analyzed only commercial banks or specific types of loans. Beck and Jonghe (2013) described the positive effects of loan concentration on commercial banks. The authors argued that commercial banks accumulate sufficient knowledge and experience in the field by focusing on loans to specific sectors over many years. This suggests that banks improve their ability to inspect and supervise loans and can reduce potential risks by identifying and addressing credit-related issues in a timely manner. Tabak, Fazio, and Cajueiro (2011) also argued that the concentration of lending to specific sectors in Brazilian banks shows that banks can enhance supervision, increase expertise in those areas, and lower bank risk while improving profitability. In this paper, we empirically examine the impact of concentrated loan portfolios on bank failures using the methodology of logistic regression. Our analysis shows that for saving banks the more concentrated the loan portfolio and the larger the number of mega loans (i.e., loans above 1 billion won), the higher the likelihood of failure. We also find that the more loans to relatively high risk borrowers and to borrowers with lower credit ratings in both the corporate and household sectors, including project financing and unsecured personal loans, the higher the probability of failure. However, mortgages with relatively good collateral turn out to have a significant negative relationship with savings bank insolvency.