The Handbook is part of the Handbook of Reagents for Organic Chemistry series, aiming at collecting articles on a particular theme that individual researchers in academia or industry can use on a daily basis. The Handbook starts with a section discussing the most important aspects of heteroarene functionalization. The introduction is followed by the alphabetical listing of the most relevant reagents drawn from the EROS database. The Editor, Andre Charette from the University of Montreal, has selected 120 reagent descriptions, many of them updated with heteroarene-specific reactions for this Handbook. Following the standard format for EROS, each article contains an overview of the synthesis and physical properties of the reagents or catalyst, conditions for its storage, and purification methods. Given the importance of heteroarenes in biology and especially in medicinal chemistry, a Handbook that focuses exclusively on heteroarene functionalization has been long overdue. This Handbook will have a broad appeal to many individuals engaged in the area of medicinal chemistry, fine chemical synthesis and industrial-scale chemistry. Key features: Builds on the success of the previously published Handbooks of Reagents for Organic SynthesisCompares the numerous new C-H functionalization reactions that have been developed in the past decadeHeteroarene functionalization is widely used in the development of pharmaceuticals and other bioactive compoundsContains listings of secondary reagents for which more information is available in the online edition