  We present mid-infrared spectro-imagery and high-resolution spectroscopy of
the Orion bar and of a region in the Orion nebula. These observations have been
obtained in the Guaranteed Time with the Circular Variable Filters of the ISO
camera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board the
European Infrared Space Observatory (ISO). Our data shows emission from
amorphous silicate grains from the entire HII region and around the isolated
O9.5V star Theta2 Ori A. The observed spectra can be reproduced by a mixture of
interstellar silicate and carbon grains heated by the radiation of the hot
stars present in the region. Crystalline silicates are also observed in the
Orion nebula and suspected around Theta2 Ori A. They are probably of
interstellar origin. The ionization structure and the distribution of the
carriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on the
basis of the ISO observations.
