The homo- and copolymerization of 3-methylene-2-pyrrolidone (3M2P) is introduced. 3M2P is readily polymerized via conventional free radical polymerization, and two reversible deactivation radical polymerization methods including reversible addition fragmentation (chain) transfer and single-electron transfer living radical polymerization. Poly(3M2P) has a high thermal stability and a very high glass transition temperature. Poly(3M2P) does not dissolve in most common organic solvents, but it has a high aqueous solubility. Cytotoxicity tests reveal that it is nontoxic to cells, even up to concentrations of 1 mg/mL. This adds poly(3M2P) to the family of water-soluble and biocompatible pyrrolidone-based vinyl polymers.