Test case prioritization techniques have been shown to be beneficial for improving regression-testing activities. With prioritization, the rate of fault detection is improved, thus allowing testers to detect faults earlier in the system-testing phase. Most of the prioritization techniques to date have been code coverage-based. These techniques may treat all faults equally. We build upon prior test case prioritization research with two main goals: (1) to improve userperceived software quality in a cost effective way by considering potential defect severity and (2) to improve the rate of detection of severe faults during systemlevel testing of new code and regression testing of existing code. We present a value-driven approach to system-level test case prioritization called the Prioritization of Requirements for Test (PORT). PORT prioritizes system test cases based upon four factors: requirements volatility, customer priority, implementation complexity, and fault proneness of the requir...