(2-Bromoethyl)oxirane is converted in 39% yield to poly-[(2-bromoethyl)oxirane] of inherent viscosity 1.99 dL/g. The AlEt3/H2O/AcAc system is a very effective initiator for the polymerization of (2-bromoethyl)oxirane. Poly[(2-bromoethyl)-oxirane] is a white elastomer, soluble in CHCl3and insoluble in CH3OH. Polyether-urethane hydrogels are prepared by the room temperature crosslinking of poly[(3-hydroxypropyl)oxirane] with aliphatic or aromatic diisocyanates. These networks absorb 100–200% of their weights in water, and can be prepared in transparent form with potential application as biomaterials or contact lenses.