In this volume recent developments in the nonperturbative aspects of string theory, duality in N = 1 string compactifications, orientifolds and F-theory as well as the matrix model description of M-theory are reported. The D-brane approach to black holes and their entropy is also discussed.The phenomenological part is devoted to the main fields of present-day astroparticle physics: supersymmetry, neutrino physics and cosmology. The two most important aspects of supersymmetry are covered: Searches for superpartners (G Kane) and mechanisms of supersymmetry breaking (G Dvali).Results from recent neutrino experiments and their implications are presented (S Pakvasa). The central issues of modern cosmology such as inflation (R Brandenberger), formation of topological defects (T Vachaspati) and dark matter (M Kamionkowski) are discussed.