  I present an overview of the results obtained by the Infrared Space
Observatory (ISO) on circumstellar material in pre-main sequence (PMS) stars.
Results obtained for embedded YSOs, Herbig Ae/Be systems and T Tauri stars are
reviewed and their connection to the disks around Vega-type systems is
discussed. Although the gas contents of the PMS environment will also be
discussed briefly, this review will mainly focus on the composition, mineralogy
and evolution of dust in these systems, and the results will be compared to
those found in other classes of objects, including solar system comets.
