  ISO observations will improve our understanding of disks around low-mass
pre-main-sequence stars in various ways. In particular, ISO can measure
simultaneously spectral energy distributions and low-resolution spectra from 2
to 12 \um of T Tauri stars with greater sensitivity, greater spectral coverage
and finer spectral resolution than available in ground-based observations or
with IRAS. We illustrate the importance of such observations for our
understanding of the disk structure and heating mechanisms, the disk evolution
(in particular the formation of gaps caused by the presence of companion stars
or large planets) and dissipation using preliminary results from PHOT and
PHOT-S for T Tauri stars in the Chamaeleon cloud.
