The high resolution IR spectrum of cyclobutane in a supersonic molecular beam was obtained for the region of 2981 to 2991 cm-1. The spectrum reveals four overlapping bands suggestive of vibrational mode coupling in the C-H stretching region. Ground -state combination differences demonstrate that these bands__ Ac_:e io For originate from 2 different ground states, the symmetric and INT IS CF-., asymmetric ring puckering states. Evidence of vibrational mode, ' coupling is present in all four bands. The coupling depends on' J both J and the symmetry of the puckering state. A model:. coupling scheme involving two qualitatively different types of y couplings is developed to explain the observed spectrum.. -----------Symmetry restrictions and the Interaction between molecular" rotation and ring puckering qualitatively accounts for the[ dramatically different coupling behavior between the two ring/ puckering states.