A review of the state of the art and trends in automation and control of copper hydrometallurgical processes is presented. Besides the great expansion of hydrometallurgical processes world-wide, there is a number of unsolved problems related to lack of instrumentation, lack of process knowledge, odd operating practices, and general lack of use of data management and processing. In general, process control of local objectives are frequently achieved, however, application of mature and new techniques, successfully adopted in other mineral processing plants, are seldom reported. In the near future it is expected that intelligent techniques will be incorporated to solve a large variety of problems. To test and evaluate new control strategies, a pilot SX/EW plant has been set up and instrumented at the Process Control Laboratory, Santa Maria University, in Chile. The control system is organized at three levels in an architecture including field controllers, PLC and PC networks. The main objectives are to deve lop and test intelligent techniques in an hybrid system, and to study measurement and supervisory control problems. It is hoped to produce reliable results that will contribute to improving the efficiency of this emerging and important process. This paper describes the current status and limitations of control of SX/EW plants and summarises where the main deficiencies lie and a proposed methodology to remedy them. © 2001 Elsevier Science Ltd. All rights reserved.