Tetrahydrofuran was polymerised with boron trifuoride etherate (BF3·Et2O) and terminated with hydrobromic acid to give the bromide-terminated prepolymer, which, on further reaction with ketal derivative of glycerol and subsequent hydrolysis, gave tetrahydroxyl-terminated polytetrahydrofuran. The prepolymer was chain-extended with tolylenediisocyanate and hexamethylenediisocyanate in six different solvents to give cross-linked polyurethane. These polymers were characterised by infrared, viscosity and thermogravimetric analysis. The glass-transition temperature, the tensile strength at break, and elongation were also determined. © 1981, The Society of Polymer Science, Japan. All rights reserved.