This chapter contains sections titled: Huisgen 1,3-dipolar cycloaddition Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) Acceleration of the Click Reaction Copper-free Click Chemistry Ruthenium-Catalyzed Azide-Alkyne Cycloaddition (RuAAC) Use of Other Metals for the Cycloaddition of Azides and Alkynes: Ni(II), Pt(II), Pd(II) Cycloaddition Reactions with Azides for the Synthesis of Tetrazoles Click Chemistry for the Synthesis of Dihydrotriazoles Cycloaddition Reactions with Azides to Give Thiatriazoles References