A supply chain has been defined as “Three or more companies (suppliers, focal company and customer) linked together by flows of products, services, information and finance, which may include manufacturing” (Mentzer, et. al. 2001). In other words, a supply chain consists of multiple firms with each firm engaging in multiple functions in a combined effort to meet common goals, while simultaneously coping with the individual firms’ needs to meet its own firm and functional goals. There are a multitude of processes, sub-processes and activities in any supply chain, whether it is made up of large or small firms. With these and perhaps other issues to deal with, one might ask, what is the probability that everything will work according to plan in a supply chain? And having posed that question, when something is not working correctly in a complex supply chain, how can management assess the problem, and equally important, determine a viable solution. Utilization of one or more of a number of supply chain diagnostic tools that have been developed may be the answer. In this chapter, a variety of tools for diagnosing potential problems in a supply chain are reviewed and discussed. These diagnostic tools vary in terms of format, complexity and cost. Quantitative approaches as well as some qualitative diagnostic tools are described. Some of these tools require less data gathering than others and are, therefore, less time consuming than others. Discussion as to when one tool versus another might be used is also included. The tools listed are suitable for either self assessment or for assessment employing a small team of facilitators. Proprietary tools employed by consulting firms as part of a consulting contract have not been included.