We propose to follow up a ground-based optical-infrared study of the
 zeta Aur system XX Oph with SWS and PHT-P observations. Our prime
 spectral targets are (i) the `PAH' features in the 6 - 8, 10.5 - 13.5
 16 - 30 micron regions, and (ii) H emission lines at 12.4, 19, 27
 microns. We will use PHT-P to carry out photometry in the range 20
 - 100 microns. Our objectives are to understand the origin and nature
 of PAH molecules in this remarkable system, to search for dust at the
 longest wavelengths, and to verify the reddening deduced from
 optical observations.