This volume documents the contributions presented at the III Scientific Meeting of the Spanish Astronomical Society (SEA). Covering a wide range of topics, the 92 contributed papers give a comprehensive overview of the current state of Spanish astronomy. The Proceedings include special reviews dealing with the cosmological evolution of star-forming galaxies, the nature of cosmic gamma-ray bursts, infrared astrophysics with ISO, and the distance scale after Hipparcos, with special emphasis on the development of the next generation of instruments to propel astrophysical research into the new century. The contents of these Proceedings thus reflect the broad interests of the Spanish astronomical community. The significance of these proceedings can hardly be exaggerated, since here, for the first time, the SEA publishes the proceedings of its own scientific meeting. The intended audience is professional astronomers and graduate astronomy students worldwide.