The rotational millimeter-wave spectrum of CH318OH has been revisited, and 162 transitions of both a- and b-types have been measured in the 119-165 GHz spectral range. The spectrum was recorded using thefrequency-modulated millimeter-wave spectrometer at the/ustus-Liebig-Universit~it in Giegen. The CH318OH transition assignments were basedon energy levels obtained from the far-infrared analysis of S. Zhao (Ph.D.thesis, University of New Brunswick, 1993) using the "Ritz" program ofG. Moruzzi et al. (J. Mol. Spectrosc. 167, 156 (1994)) for direct energylevel fitting. The relatively low residuals between calculated and observed frequencies highlight the good quality of the results from this program. The newly measured transitions combined with those existent in the literature have been included in least-squares fits to improve the set of rotational,torsional and centrifugal distortion constants for O-18 methanol.