Many of the tasks of the clinical laboratory involve the application of knowledge and experience to patient-specific problems. Expert systems that have ready access to patient data and expert knowledge have the potential to support many laboratory processes, especially those that involve the repetitive and reasonably predictable application of knowledge. Quality assurance and utilization improvement efforts requiring constant vigilance and surveillance of an array of laboratory processes especially may benefit. Expert system technologies, trends of their use in the clinical laboratory, their role in the total testing process, and their potential for influencing physician use of the laboratory through timely feedback are discussed.