This seminar covers the state of the art and the full spectrum of topics in defect diagnosis ranging from the basic concepts, real world application to future challenges. After a brief review of the basic concepts and applications of diagnostics over the life-cycle of a product, we will discuss the established diagnosis procedures - fault dictionaries, post-test fault simulation, and harware-based backtracking. Next, we will cover recent enhancements and advanced diagnosis topics, including methods forlocating defects such as opens, shorts, and leakage in transistor-level circuits, approximation techniques for identifying unmodelled faults, deductive analysis, Iddq-based diagnosis, diagnosis for delay-faults, Scan-chain diagnosis, BIST-based diagnosis, and design-for-diagnosability techniques. Then we will focus on Silicon debug techniques, design-for-debug techniques, and applications to yield improvement. We will also describe succesful diagnosis methods used in real industrial products, industrial experiences, and case studies. Finally we will discuss future directions and challenges.