This volume is the compilation of invited lectures presented at the Spring School "Problems of Modern Quantum Field Theory" held in Alushta (USSR) April 24-May 5 1989, organized by the Institute for Theoretical Physics (Kiev) and Landau Institute for Theoretical Physics (Moscow). Approximately one hundred physicists and mathematicians attended lectures on aspects of mod- ern quantum field theory: Conformal Field Theory, Geometrical Quantization, Quantum Groups and Knizhnik-Zamolodchikov Equations, Non-Archimedian Strings, Calculations on Riemannian Surfaces. A number of experts active in research in these areas were present and they shared their ideas in both formal lectures and informal conversations. V. Drinfeld discusses the relation between quasi-Hopf algebras, conformal field theory, and knot invariants. The author sketches a new proof of Konno's theorem on the equivalence of the braid group representations corresponding to R-matrices and the Knizhnik-Zamolodchikov equation. The main ideas of quantum analogs of simple Lie superalgebras and their dual objects - algebras of functions on the quantum supergroup - are introduced in the paper by P.P. Kulish. He proposes the universal R-matrix for simplest superalgebra osp(2/1) and discusses the elements of a representation theory. In the paper by A. Alekseev and S. Shatashvili the correspondence between geometrical quantization and conformal field theory is established. It allows one to develop a Lagrange approach to two-dimensional conformal field theory. The authors also discuss the relation to finite R-matrices.