The performance based ANSI/ISA S84.01 and IEC 61508 standard provide overall risk based safety life cycle models for industrial processes. Among other guidance, they provide the basic methodology and guidelines for the identification of safety instrumented systems necessary for a process to meet the established target risk levels. In order to arrive at risk based solutions, many practical issues need to be addressed Such issues include identification of target risk levels, identification of hazardous events associated with the process tinder consideration, establishing the existing risk associated with the process, and selection of appropriate non-instrumented and instrumented safety systems to meet the target risk. This paper outlines the basic methodology, and discusses some of the related issues mentioned above. Further, it provides a few methodologies to establish the requirements of the safety instrumented systems and their safety integrity levels.