N-Oxide compounds are very important intermediates in synthetic organic chemistry as well as in the chemical industry. Numerous efforts have been devoted to the development of efficient approaches for the C À H bond activation and functionalization of N-oxides in recent years, including arylation, alkenylation, alkylation, acyloxylation, amination, amidation and sulfonylation. In this review, recent advances in this area are summarized and their mechanisms are discussed.