The controversial question of whether the majority of the narrow
absorption lines observed in QSO spectra represent cosmological
intervening systems or ejecta from the QSO themselves is settled. QSO
absorption line spectroscopy, initially a mere technique, has matured
into an essential extragalactic research tool for understanding the
content of the Universe at redshifts between 0 and 4, and beyond. The
only previous important meeting devoted to "QSO Absorption Lines" was
held in May 1987 at the Space Telescope Science Institute in Baltimore,
Maryland, U.S.A. Since that time, nearly a decade ago, research has been
ex- tremely active in this now well-established field of astrophysics.
Theoretical stud- ies and simulations have taken advantage of the
constant progress in computer technology, and during these last few
years, the observational results have bene- fited largely from the new
facillities offered by the Hubble Space Telescope in the UV wavelength
range and the Keck Telescope for high-resolution spectroscopy.