p-vinylbenzylphosphonic acid was prepared by means of the Arbuzov reaction between triethyl phosphite and p-chloromethylstyrene followed by silylation with bromotrimethylsilane and methanolysis. The product, which is readily cross-linked, is stabilized as dicyclohexylammonium salt. Radical-initiated polymerization occurs readily; homo- and copolymers found are slowly cross-linked upon releasing dicyclohexylamine.