The addition of DCPA to a variety of phenylethylenes has been examined. After a short induction period the reaction proceeds rapidly and exothermically to give high yields of N- chloro adducts, which afford the corresponding phosphoroamide derivatives upon reduction with sodium pyrosulphite solution. Addition of DCPA to methylstyrenes as well as trans- stilbene is nonstereospecific and in the latter case evidently subject to steric retardation. ...