At the beginning of this article an in-depth comparison of electrophilic and nucleophilic aromatic and heterocyclic substitution processes examines their scopes of applicability in a new light. In the subsequent parts, recent progress in the area of halide and hydride displacement from pyridines is highlighted. Particular attention is paid to the leaving group aptitudes of fluoride and chloride, to the effect of 'passive' substituents on the reaction rates, and to the control of the relative reactivity at halogen-bearing 4-versus 2-(or 6-)positions.