As a part of our interest in intramolecular hydrogen-bonding problems the microwave spectrum of ethylene glycol was investigated. Previously, electron diffraction investigations [1, 2] have shown that the preferred conformation of the free molecule has the two C-O bonds gauche to one another, and the dihedral angle between the two OCC planes is about 65°. Moreover, the infrared spectrum [3] of gaseous ethylene glycol presents strong evidence for the presenee of intramolecular hydrogen bonding stabilizing the gauche rotamer. In an attempt to assign the microwave spectrum the following procedure was used. A plausible structure of the gauche form was first assumed and th~ rotational constants calculated to be about A = 16.4 GHz, B = 5.1 GHz, and C = 4.4 GHz, respectively. A rigid rotor spectrum was then predicted with these rotational constants and a very thorough search was made for low J a-, b-, and c-type transitions in the 8-38 GHz spectral region. However, no lines with app~opriate Stark effects were found in the predicted frequency ranges, and we therefore feel that it is very unlikely that all three dipole moment components follow rigid rotor selection rulcs. lnstead of the expected rigid rotor spectral features, a very unusual spectrum was revealed. Of about 600 transitions* of medium and strong intensities occurring in the examined spectral range, more than 200 of the strongest lines fall in the 16-19 GHz range with the majority centered around 17.1 GHz. Study of the unresolved Stark effects of these as well as of the great majority of the other intense lines strongly indicated that they are high J transitions. Only the 12 lines ofTable 1 were found to possess resolved Stark lobes with relative intensity features characteristic for R-branch transitions [4]. Attempts to fit these lines to a rigid rotor spectrum of the gauche rotamer proved impossible.