This study evaluates the effect of consolidation on the efficiency of banks in Nigeria and also examines the effect of consolidation on the size/spread of loans advanced by banks and on the profitability of intermediation of banks in Nigeria. The study used a period of six years from 2003 to 2008 comprising three years pre and post consolidation periods.The population was the whole 24 banks while the sample was six banks selected using

stratified sampling technique. The study utilized only secondary data obtained through annual reports, and CBN Banking Supervision. The techniques employed for data analysis in this study are Data Envelopment Analysis (DEA) with four by three input/output variables model, to determine the efficiency, Descriptive Trend analysis, and T-test for testing the hypotheses formulated. The findings of the study show that Consolidation have significant positive effect on the efficiency, size/spread of loans advanced and on the intermediation profitability of banks in Nigeria. In view of the major findings and policy implications of the study, we concluded that consolidation play significant role in enhancing efficiency, increasing size of lending and lending profitability of banks in Nigeria. The study therefore recommends that the management of banks should work hard to ensure that adequate measures had been put in place to determine the operational /intermediation efficiency of their banks so that effective and efficient utilisation of resources would be maintained.