The Fifteenth Jerusalem Symposium reflected the high standards of the former international scientific meetings, which convene once a year at the Israel Academy of Sciences and Humanities in Jerusalem to discuss a specific topic in the broad area of quantum chemistry and biochemistry. The topic at this year's Jerusalem Symposium was intramo­ lecular dynamics, a subject of central interest for theoreticians, che­ mists and biologists. During the last two decades, there has been remarkable pro­ gress in our understanding of time dependent phenomena. The development and application of the modern techniques of quantum mechanics and sta­ tistical mechanics to excited-state dynamics and to chemical and biophy­ sical systems constitutes a fast developing current research area. The main theme of the Symposium was built around a conceptual framework for the elucidation of photophysical and photochemical phenomena in atoms, molecules, van der Waals complexes and clusters, condensed phases, poly­ mers and biological supermolecules. The interdisciplinary nature of this research field was deliberated by intensive and extensive interactions between scientists from different disciplines and between theory and experiment. This volume provides a record of the invited lectures at the Symposium.