Accumulation of theoretical experience, on one hand, and experimental data, on the other, resulted in a considerable progress in weak interactions. The current literature concentrates mainly on such issues as the study of the Kobayashi-Maskawa matrix and the application of quantum chromodynamics to concrete processes. Here I discuss the most interesting developing fields referring both to old (light) and new (heavy) hadrons. The first part is devoted to oscillations and other processes of the second order yielding information on Vbu and the t quark mass. The second and the largest part describes the modern QCD-based approaches in the traditional problems (K meson and hyperon physics) and in new problems associated with heavy quarks.