Three new heavy water rotational absorption lines have been observed in the microwave region. One of these lines and another line previously observed by McAfee have been identified as HDO lines by a study of the variation of their intensities with isotopic molecular concentration. By interpreting their Stark structure, the two HDO lines are assigned as follows: HDO:8−1→80 at 24 884.85 Mc/sec and HDO:6−2→7−6 at 26 880.47 Mc/sec. In addition, results on the Zeeman spectra of the two identified HDO lines are presented.