The foundations of the use of statistical-mechanical equations of motion, in particular the Pauli equation, for the description of intramolecular processes and molecular fragmentation are discussed briefly. Quantum-mechanical trajectories for model systems illustrate how the statistical behaviour may emerge from the dynamical equations of motion. Product state distributions resulting from the fragmentation of strongly coupled, metastable intermediates in chemical-activation experiments can be calculated by using restricted equipartition, which applies as the long-time limit of the Pauli equation. A simple Pauli-equation model is proposed to calculate lifetimes of metastable intermediates. The consequences of the finite rate of intramolecular relaxation processes for the specific rate constants for fragmentation and possible deviations from microcanonical equilibrium are explored.