Samples of hydroxy-terminated and amine-terminated (polytetrahydrofuran; PTHF) of various molecular weights were prepared by the polymerization of tetrahydrofuran with boron trifluoride ethereate in three steps. These PTHFs were characterized by molecular weight, hydroxyl number, amine equivalent and i.r. They were then converted to isocyanate-terminate prepolymers and then cured with diols and diamines. The resulting polymers were characterized by i.r., viscosity and density measurements. © 1989.