Using detailed Japanese credit data, we test for the existence of a credit market hierarchy. Empirical tests indicate that firms with information problems are more likely to carry higher proportions of relationship loans from main banks than non-main banks, holding constant risk and control factors. We further examine credit specialization on the part of lenders by testing the relationship between client firms' information and risk characteristics and the concentration of loans obtained from depository institutions versus other financial institutions. However, no significant differences in information superiority between these two types of financial institutions are found. We conclude that our evidence supports the credit market hierarchy hypothesis for Japanese main banks in particular but not depository institutions in general.