We present a new study of the millimeter wave spectrum of the lowest two conformers of the 1,3-propanediol (CH 2 OHCH 2 CH 2 OH) molecule. The new measurements involving rotational transitions with J up to 65 and K a up to 30 for conformer I and J up to 59 and K a up to 29 for conformer II have been carried out between 49 and 237GHz using the Kharkov millimeter wave spectrometer. The new data were combined with previously published measurements and fitted using a model that assumes a symmetric potential energy surface with two minima between which the system tunnels. The final fit included 19 parameters for conformer I and 23 parameters for conformer II with weighted root-mean-square deviations of 0.81 and 0.73 achieved for datasets consisting of 3384 and 2947 line frequencies belonging to the ground states of conformer I and conformer II, respectively. The millimeter wave spectra of both conformers reveal a rather strong influence of the Coriolis type perturbation, which previously was not taken into account in the analysis of the 1,3-propanediol spectrum.