The decision to chose one RTOS over another or whether to even use an RTOS is dependent on many factors. Careful consideration must be given to issues such as performance, determinism, availability, cost, system resources, available support, and even access to source code in some regulatory environments. This paper proposes to help developers identify and quantify what their system’s real-time requirements are to help them make a decision regarding what if any RTOS technology is appropriate for their application. The paper will cover: Systems analysis techniques for quantifying the real-time requirements of a particular application; Requirements for deterministic performance versus requirements for throughput performance; A survey of common RTOS offerings and the features and performance they support (according to their published specifications). The paper will also discuss emerging RTOS standards for vertical applications such as OSEK and ITRON.