  The giant molecular cloud Sagittarius B2, located near the Galactic Centre,
has been observed in the far-infrared by the ISO Long Wavelength Spectrometer.
Wavelengths in the range 47-196 microns were covered with the high resolution
Fabry-Perot spectrometer, giving a spectral resolution of 30-40 km/s. The J=1-0
and J=2-1 rotational transitions of HD fall within this range at 112 microns
and 56 microns. A probable detection was made of the ground state J=1-0 line in
emission but the J=2-1 line was not detected above the noise. This allowed us
to calculate an upper limit on the temperature in the emitting region of
approximately 80 K and a value for the deuterium abundance in the Sgr B2
envelope of D/H=(0.2-11)x10^-6.
