Vinylic nucleophilic substitution via a concerted bimolecular mechanism (S_NV 2), which has long been rejected as a possible pathway, has recently been found to be feasible both theoretically and experimentally. Two S_NV 2 mechanisms are possible : one is designated as S_NVσ where nucleophilic attack takes place in a molecular plane at the σ^* orbital resulting in inversion of configuration, while the other as S_NVπ which involves out-of-plane π^* attack of a nucleophile leading to stereochemical retention. Both modes of the concerted S_NV 2 reactions were found for vinyl iodonium salts, and detailed mechanistic investigations are summarized. Intramolecular S_NVσ reactions were more often observed, and applied to some synthesis of cyclic compounds. Those observations are rationalized by high level ab initio MO calculations.