Tyrosine phosphorylation is a rapid and reversible protein modification catalyzed by the yin and yang activities of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). A multitude of PTPs have been implicated in human disease, with a growing number of PTPs now known to play major roles in prevalent metabolic diseases including obesity and type 2 diabetes. Recent studies into PTP function in the context of metabolism highlight the importance of understanding the specific substrates and binding partners of these enzymes, the regulation of PTP activity, and the cell/tissue specificity of PTP functions. This volume contains chapters which highlight many aspects of PTP function in the context of metabolism.--