We have recently made a synthetic breakthrough in the area of heterocyclic organophosphorus chemistry that has facilitated the isolation of two unusual classes of phosphorus-carbon ring systems. Specifically, we have discovered that the reaction of a phosphaalkene with electrophiles (HOTf or MeOTf) results in either a three- or a four-membered ring. The intermediacy of phosphenium-like and methylenephosphonium ions has been confirmed spectroscopically. The successful isolation of these unprecedented species is important to the chemistry of phosphorus. In addition, this work may have broader implications to the analogous, currently unknown, nitrogen ring systems.