The Workshop on Operator Theory and Its Applications, IWOTA 95, was held at the University of Regensburg, Germany, July 31 to August 4, 1995. It was the eighth workshop in the series of IWOTA (International Workshops on Operator Theory and Applications). The conference covered different aspects of linear and nonlinear spectral problems, starting with problems for abstract operators up to spectral theory of ordinary and partial operators, pseudodifferential operators, and integral operators. The workshop was also focussed on operator theory in spaces with indefinite metric, operator functions, interpolation and extension problems. The applications concerned applications to mathematical physics, hydrodynamics, magnetohydrodynamics, quantum mechanics, astrophysics as well as the theory of networks and systems. The papers in the two volumes of the proceedings of IWOTA 95 bring the readers up to date on recent achievements in these areas. This volume contains the contributions to different aspects of operator theory and its applications. Its companion volume (OT 102) is focussed especially on differential and integral operators. The set will be of practical use to a wide-range readership in pure and applied mathematics, physics and engineering sciences.