Results of a detailed study of group transfer additions of methyl(phenylseleno)propanedinitrile (4) to a wide variety of alkenes are reported. For example, heating of 4 (60 degrees C) with 1-hexene and AIBN produces (2-(phenylseleno)-hexyl)methylpropanedinitrile in 97% yield. Reagent 4 adds in high yields to monosubstituted styrenes, enol ethers, enol acetates, enol sulfides, enamides, and enol imidazoles and carbazoles. Additions to many classes of 1,2-disubstituted alkenes also occur, and modest to good levels of 1,2-asymmetric induction are observed in the selenium transfer step. Oxygen- and sulfur-substituted alkenes produce anti products, and N-substituted alkenes produce syn products. The proposed mechanism involves radical addition followed by phenylselenium group transfer, and it is shown that radical additions to certain classes of disubstituted alkenes can be reversible. Additions to trisubstituted alkenes fair, probably because of this reversibility. Competition studies provide a relative reactivity scale of alkenes toward the electrophilic methylpropanedinitrile radical. Finally, a series of transformations serve to illustrate some synthetic possibilities for the products of these selenium transfer addition reactions.