In this paper, we present a knowledge-based approach to dead-time estimation suitable for process control systems. The approach is based on the use of relay feedback, and a self-contained module for dead-time estimation is developed which is based on suitable heuristics derived and analysed in the paper. Knowledge-based techniques are adopted and this development forms a module of a larger project for development of an intelligent process control system. The paper also includes the results of real-time experiments to estimate the dead-time of a pilot scale coupled-tanks system.