Test automation can be thought of as "writing software to test other software”. Using one of the commercially available automated testing tools, test scripts are written that drive the application under test -- execute keyboard, mouse actions and background processing -- and verify application responses and behavior just as a human would. Automated testing can reduce or eliminate the drudgery and repetition associated with some manual tests, decrease the time required to test and make your tests more consistent and repeatab le. Automation testing also increases the quality of the product and produces early fault tracking during the testing phase. Convergys Test Automation Team has developed an Advance Data Driven Testing (ADDT) approach by using the Test Automation Engine, which drives WinRunner based on the input provided by the tables. This technique is used to test our highly complex PC based Billing Application for the Client and also for Background testing. The approach has been successfully implemented in System Test Organization in Convergys for the regression and new features testing. In the last two years, it has been proven that Automation Testing can improve the reliability and the quality of our software products and reduce the man-hours needed. Automation testing also helps us to detect faults in earlier stages of software release cycles, which reduces the bug fixing cost dramatically. This technique is generic and can be used for any PC based Client/Server application or web application by modifying the Test Automation Engine.