The additions of cations, radicals, and radical cations to nitriles, in particular acetonitrile, have been investigated. The literature reports examples of all of these reactions and on the basis of these reports as well as our own experimental and theoretical results, conclusions can be drawn concerning the preferred mode of addition to the nitrile moiety. There is a clear preference for cations to add to the nitrogen of the nitrile. Similar behavior is observed with radical cations. Radicals, on the other hand, prefer to add to the carbon of the nitrile. Examples of reactions that proceed via these preferred modes of addition, as well as some examples of reactions that do not follow these general trends, are discussed. The experimental results are compared to those of ab initio molecular orbital calculations.