Book excerpt: This volume details the current understanding of roles and regulation on histidine phosphorylation, describing methods for the characterization of protein phosphorylation on histidine. Chapters guide readers through in vitro systems, cell-based systems, comprehensive background review articles on histidine kinases and phosphatases. 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. Authoritative and cutting-edge, Histidine Phosphorylation: Methods and Protocols aims to ensure successful results in the further study of this rapidly growing field.