This paper presents the development of an interface between an expert system and a data base management system. The flexibility provided by such interface is shown to be very useful for civil engineering applications. An example application is developed in this paper that applies this interface to the management of retaining walls. The different relational data bases store most of the required information. The inventory data base stores identification information, the inspection data base stores historical condition data gathered by inspections, and the replacement data base stores information needed to perform a replacement cost analysis for a retaining wall. The expert system, on the other hand, is used to diagnose the possible reasons for the failure of a retaining wall. The development of the data base management system, the expert system, and the interface between them is discussed, along with the restrictions imposed by the software chosen for this example application.