The development in the techniques for obtaining synovial tissue biopsy, especially through arthroscopy, have resulted in greater access to high-quality synovial tissue. The use of immunohistochemistry in arthritis research has greatly furthered our understanding of the varied immunological and biochemical pathways involved in inflammatory arthropathopies such as rheumatoid and psoriatic arthritis. Immunohistochemistry provides a strikingly visual narrative of the essential elements involved in inflammatory arthritis, from the infiltrating inflammatory cells (e.g., T-cells, macrophages, B-cells, and neutrophils), their products (e.g., cytokines, metalloproteinases) and their varied receptor molecules. This chapter describes the standard three-stage immunoperoxidase technique used in our laboratory and widely in the literature. Some problems that may be encountered and how they may be overcome are commented on. Also described is a method for dual-labeled immunofluoresence staining.