This is the first meeting in the series of International GLAST Symposia. The Gamma-ray Large Area Space Telescope, GLAST, is a mission to discover and study cosmic gamma-ray sources in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in Fall 2007, GLAST will open a new and important window on a wide variety of high-energy phenomena, including black holes and active galactic nuclei; gamma-ray bursts; pulsars; the origin of cosmic rays and their relation to supernova remnants; probes of the optical-UV EBL; new source classes; solar physics; and searches for signals of hypothetical new phenomena such as particle dark matter annihilations, extra dimensions, Lorentz invariance violation, and other relics from the Big Bang. The first Guest Investigator Cycle will start in 2007, with proposals due soon after the Symposium. More information about the mission can be found at http://glast.gsfc.nasa.gov and at links therein. The first Symposium will focus on the new scientific investigations enabled by GLAST, mission and instrument characteristics, analysis tools and opportunities for guest investigators, and coordinated observations and analyses. It is expected that the second Symposium will occur approximately 18 months later.