Rapid growth in medical knowledge and improvements in laboratory instruments have created a need for a reliable computer-assisted method of assessing data. Pulmonary Consult was designed as a productivity tool for physicians and structured to support individual configuration and require minimal user training. A hierarchical, rule-based approach was adopted to permit easy expandability and modification of decisions. The system was designed to achieve reliable performance even in the presence of insufficient or inconsistent data. Validation was achieved by comparing general disease classification and severity degrees with those of several individual physicians.