This volume contains the proceedings of the 12th International Conference of the Entity-Relationship Approach, held in Arlington, Texas in December 1993; it contains the revised versions of 42 papers selected for presentation at the conference from a total of 87 submissions. The volume presents many of the most important results on the ERA published since the predecessor conference ER '92. It is organized in sections on object-oriented models, query languages, applications of the ER model, knowledge-based modeling, data modeling, schema integration, reuse and reengineering, integrating ER and object-orientation, conceptual clustering, modeling time and data semantics.