Multiphase reactors are becoming an important subject as a result of numerous applications in various fields ranging from chemical and petrochemical to food, biological and pharmaceutical (FBPl en gineering, namely in the hydrodesulfurization of petroleum, produc tion of antibiotics and wastewater treatment. The importance of the subject is measured by the increasing num ber of publications and meeting sections dedicated to it. Therefore an Advanced Study Institute on Multiphase Chemical Reactors was held in Vimeiro, Portugal from 18 to 30 August 1980, following an International Symposium on Chemical Engineering of Gas-Liquid-Solid Catalyst Reactions, held in Liege, 1978. The purpose of this NATO ASI was to present a didacted approach to multiphase reactor design, through the interaction among hydro dynamics, reaction and transport processes. The lectures delivered there are compiled in two volumes. In the first volume an overview of the field is presented, followed by a detailed analysis of the fundamental concepts (interphase mass transfer models, mass transfer with chemical reaction, theory of residence time distributions and micromixing phenomenal.Numerical methods are often required to solve the mathematical models involved; so a chapter is dedicated to this subject followed by a discussion of steady-state multiplicity and stability. Finally, a section with special applications of multiphase reactors is included, presenting topics on biological reactors, emulsion po lymerization, supported liquid phase catalyst and enhanced oil re- VI covery."