This paper reviews the capabilities and application of the CONSTRUCTION PLANEX system. This knowledge-based expert system assists in the selection of construction technology, the definition of work tasks, the estimation of required resources and durations, the estimation of costs, and the preparation of a project schedule. The system has been applied in laboratory simulations in three ways: interactively as an intelligent assistant, independently as an automated planner, and as part of an integrated building design environment. CONSTRUCTION PLANEX can plan for the excavation and structural erection of concrete and steel building; example applications have ranged from two to twenty stories. Provisions are included for expanding the knowledge base to consider other functional elements or facility types. Descriptions of system architecture, knowledge representation scheme, control procedures, and applications are included.