We analyze what drives bank efficiency in the transition countries of Central Europe and compare the results with those for the United States. This paper is one of the few that use data envelopment analysis for the computation of efficiency scores in transition countries, and, to our knowledge, it is the first to explore systematically how different specifications of data envelopment analysis affect the results. Our findings corroborate the common wisdom that foreign-owned banks operating in transition countries are more efficient than domestic banks. While in the United States large banks are in general more efficient, the result for transition countries depends on the design of data envelopment analysis.