An investigation of the intramolecular cyclopropanation reactions of alpha-diazo-beta-ketonitriles is reported. These studies reveal that alpha-diazo-beta-ketonitriles exhibit unique reactivity in their ability to undergo arene cyclopropanation reactions; other similar acceptor acceptor-substituted diazo substrates instead produce mixtures of C-H insertion and dimerization products. alpha-Diazo-beta-ketonitriles also undergo highly efficient intramolecular cyclopropanation of tri- and tetrasubstituted alkenes. In addition, the alpha-cyano-alpha-ketocyclopropane products are demonstrated to serve as substrates for S(N)2, S(N)2', and aldehyde cycloaddition reactions.