The far-infrared spectra of tetrahydrofuran-3-one show ring-bending (100-120 cm(-1)), ring-twisting (227-237 cm(-1)), difference (115-137 cm(-1)), and overtone (200-225 cm(-1)) bands. Calculations for the two-dimensional potential energy surface governing the twisting and bending motions were carried out. The minima of the potential surface correspond to twisted conformations with twist angles of approximately +/-35 degrees. The barrier to planarity is in the 1500 to 2000 cm(-1) range. No saddle points corresponding to bent structures are present for the surface. A potential energy surface for the S-1(n,pi*) excited state, based on previous fluorescence excitation data, was also calculated. The latter has an assumed barrier to planarity of 1400 cm(-1) and a barrier to pseudorotation of 880 cm(-1).