The proceedings of the 4th International Conference on Sin­ tering and Related Phenomena, contained in this volume, have been broadened in scope to include the phenomena of sintering and coa­ lescence of catalytic materials dispersed upon refractory oxides. For it has long been recognized within the circles of chemists and chemical engineers working in the field of catalysis that one of the chief causes of the decline in heterogeneous catalytic activity and/or selectivity is, indeed sintering, or perhaps using a better term, coalescence of the supported catalytic metal and compounds thereof. Essentially catalytic deactivation by sintering is now weIl recognized as Ostwald ripening; which of course is a phenome­ non familiar to scientists grappling with the problem of sintering of powder compacts. The 4th Conference at Notre Dame marks the first occasion at which scientists and engineers of each discipline were assembled in the same room to exchange views on these phenome­ na of mutual concern. In the wake of the Conference at Notre Dame, all parties acknowledged the synergistic benefit which issued from this exchange, both at the formal and informal level. All were persuaded that signal benefits will be realized by a continuation of this collab­ oration in the form of future sintering conferences in which both powder metallurgists and catalytic scientists and engineers would participate.