ISO Observations of Pre-Main Sequence and Vega-type Stars

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.