This study aims to determine the effect of Loan to Deposit Ratio (LDR), Capital Adequacy Ratio (CAR), Operating Income Operating Expense (BOPO), and Company Size both simultaneously and partially to Non Performing Loans (NPL) in Conventional Commercial Banking Companies registered on the Indonesia Stock Exchange (IDX). The study population is conventional general banking companies listed on the BEI 2010-2016 as many as 42 companies with purposive sampling technique sampling obtained 27 company. The analytical method used is multiple linear regression analysis with a significance level of 0.05. The results showed that simultaneously LDR, CAR, BOPO and Company Size affect NPL. Partially LDR, and CAR have no effect on NPL, while BOPO and Size of Company have significant positive effect to NPL.