Diagnostic problem solving forms a major part of the operator’s activity in complex chemical processes. It cannot be overemphasized that training operators on fault diagnosis and developing appropriate corrective strategies will help minimize process upsets, and thereby improve the reliability and safety of the plant. An intelligent operator training framework has been proposed and implemented to improve training effectiveness for diagnostic problem solving. A dynamic simulator coupled with an intelligent computer-based tutor constitutes the intelligent training system (ITS). It helps operators to organize system knowledge and operational information including symptom-cause relationship, and may enhance their performance. Our learning environment is composed of an interactive, real-time simulation of a chemical process plant, a computer model of expert operators, components that allow for automatic evaluation and coaching of the trainees in order to improve their diagnostic skills, and graphical user interfaces. To make our intelligent training system more effective, the process-related information/explanations including digraph-based symptom-cause relation are supplied through intelligent hypermedia interface. This system can also be used as an on-line assistant of process operators and for the training of remedial actions, and they are part of further enhancements being planned.