From the Foreword Pyrometallurgy emerged as one of the strongest areas in the technical program of COPPER 91 - COBRE 91, following the trend established at COPPER 87. The forty-five papers included in this volume, written by authors from sixteen different countries, representing all the continents, show that these symposia are recognized worldwide as one of the industry's important pyrometallurgical forums. A number of these papers report on the modernization of existing smelters in recent years to comply with increasingly stringent environmental regulations. As a result of such concerns, flash and bath smelting processes have almost completely replaced reverberatory furnaces. This trend has been associated with more extensive and intensive use of oxygen in pyrometallurgical processes. However, industry has been reluctant to add new capacity. Overcoming this bottleneck will give pyrometallurgists opportunities to engineer even more environmentally acceptable and energy- efficient smelters. Great interest in the conservation of the environment and of natural resources is further reflect ed in several papers which address these issues directly. These will continue to be important topics in the pyrometallurgical agenda of the next few years. Pyrometallurgical process modelling and control are also rapidly expanding subjects. COPPER 91 - COBRE 91 provided a forum to discuss revitalized interest in the study of chemical equilibria, increased research efforts in process kinetics, and the need for sturdy, reliable sensors to measure the temperatures and chemical potentials of melts and hot gases, in some cases, on a continuous basis. This has become a most challenging and promising field for the pyrometallurgical profession, in which vigorous activity will undoubtedly take place in the near future. Tackling such challenges as these requires strengthening the professional ranks with a steady stream of well educated young graduates. Unfortunately, in the recent past, extract