Cohomology of arithmetic groups, automorphic forms and L-functions -- Limit multiplicities in L 2(??G) -- Generalized modular symbols -- On Yoshida's theta lift -- Some results on the Eisenstein cohomology of arithmetic subgroups of GL n -- Period invariants of Hilbert modular forms, I: Trilinear differential operators and L-functions -- An effective finiteness theorem for ball lattices -- Unitary representations with nonzero multiplicities in L2(??G) -- Signature des variétés modulaires de Hilbert et representations diédrales -- The Riemann-Hodge period relation for Hilbert modular forms of weight 2 -- Modular symbols and the Steinberg representation -- Lefschetz numbers for arithmetic groups -- Boundary contributions to Lefschetz numbers for arithmetic groups I -- Embedding of Flensted-Jensen modules in L 2(??G) in the noncompact case.

Cohomology of arithmetic groups serves as a tool in studying possible relations between the theory of automorphic forms and the arithmetic of algebraic varieties resp. the geometry of locally symmetric spaces. These proceedings will serve as a guide to this still rapidly developing area of mathematics. Besides two survey articles, the contributions are original research papers.