Motivated by public policy debates about bank consolidation and conflicting theoretical predictions about the relationship between bank concentration, bank competition and banking system fragility, this paper studies the impact of national bank concentration, bank regulations, and national institutions on the likelihood of a country suffering a systemic banking crisis. Using data on 69 countries from 1980 to 1997, we find that crises are less likely in economies with more concentrated banking systems even after controlling for differences in commercial bank regulatory policies, national institutions affecting competition, macroeconomic conditions, and shocks to the economy. Furthermore, the data indicate that regulatory policies and institutions that thwart competition are also associated with greater banking system fragility.