Plant operation is an advanced activity of a knowledge intensive system composed of various process equipment items, measurement and control instruments, and human operators. Many studies have investigated various aspects of plant operation in the areas of chemical engineering, control engineering, human factors, and so on. However a more interdisciplinary approach is necessary to solve problems in actual and future plant operations. In this paper, we will introduce activities related to plant operations in Japan. We will describe some results obtained from collaborative studies between industry and academia. These results include design and evaluation methods of human interfaces in plant operation, computational models of the human information processing of plant operators, and psychological approaches to measure the mental state of human operators, which have a great influence on the human performance. We are continuing to apply these results to create safer and more responsible plant operations in today's rapidly changing economic and social environment.