Performance specifications define the functional requirements for the product, the environment in which it must operate, and interface and interchangeability characteristics. A performance specification states requirements in terms of the required results. However, a performance specification does not state the methods for achieving the required results. They translate operational requirements into more technical language that tells the manufacturer: what will be acceptable product performance, and how that product acceptability is determined. Systems Engineering professionals can make use of the performance specification process to include those items which will verify implementation of controls and validate the elimination or mitigation and control of a variety of hazards. This paper discusses the history and provides an overview of the Department of Defense Performance Specification process. This paper will also provide guidance to the systems engineering professional in writing safety-related performance specifications and how to best use this process to the validate potential hazards have been eliminated or controlled.