The free jet millimeter wave spectrum of the 2,3-dihydrofuran-argon molecular complex was investigated in the 60-78 GHz frequency range, Only one of the two possible conformers due to the puckered configuration of isolated 2.3-dihydrofuran was observed. Estimates of the geometry and of the van der Waals interaction potential, and their relation to the ring puckering motion, are given. (C) 1997 American Institute of Physics.