  Chloromethane is the only organochloride detected in space to date. Its
recent observation towards the low-mass protostar IRAS 16293-2422 with ALMA
offers a prompt for new laboratory studies of CH$_3$Cl and its isotopologues.
Here, we report the investigation of the rotational spectrum of monodeuterated
chloromethane CH$_2$DCl in the frequency region between 90 and 300 GHz. The
measurements have been carried out with a frequency-modulation millimeter-wave
spectrometer, arranged to perform saturation spectroscopy. From the analysis of
hyperfine-resolved spectra of the two chlorine isotopologues CH$_2$D$^{35}$Cl
and CH$_2$D$^{37}$Cl, consistent sets of accurate spectroscopic parameters have
been obtained. This work provides reliable spectral predictions which can be
used to guide radio-astronomical searches of CH$_2$DCl in the interstellar
medium and represents a solid base for future analyses of high-resolution
infrared spectra of monodeuterated chloromethane.
