This book provides coverage, methodology, and laboratory protocols on the more essential aspects of protein tyrosine phosphatase (PTP) function and regulation, including the use of standardized in vitro functional assays, suitable cell systems, and animal and microorganism models. Chapters covering state-of-the-art technical approaches suitable to decipher the physiologic roles of PTPs, and their involvement in tissue-specific functions, are also included, which will be of utility for both newcomers and experienced researchers in the field of tyrosine- and phosphoinositide- phosphorylation/dephosphorylation. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls.