Objective - The objective of this paper is to determine the impact of Capital Adequacy Ratio (CAR), Loan to Deposit Ratio (LDR), Operational Efficiency proxies by Operational Expense to Operating Income Ratio (BOPO)and Non-Performing Loan (NPL) towards bank profitability proxies by Return on Assets (ROA). Methodology/Technique - Purpose samplingis applied to gather samples of the banking sector that was listed on the Indonesia Stock Exchange for the period of 2012 - 2014. Multiple regression analysis was used to analyse data. Findings - The F test result shows that CAR, LDR, BOPO, and NPL simultaneously, have a significant impact towards ROA. This means that the model can be used to predict bank profitability. It is also deduced that Operational Efficiency proxies by Operational Expense to Operating Income Ratio has a significant impact towards banking profitability. Novelty - This paper suggests that banks perform lending selectively and banks maintain the level of non-performing loans to be low in order to manage the risks and to improve their profitability as a means of increasing public confidence level. Type of Paper Empirical Keywords: Capital Adequacy Ratio; Loan to Deposit Ratio; Non-performing Loan; Operating Expense to Operating Income; Return on Assets. JEL Classification: D81, G21.