Contrary to conventional databases the conceptual schema of an object-oriented database contains the description or the operations on the data next to the description of the structures of the data which are shared by several application programs. Therefore a design method for the conceptual schema of an object-oriented database must consider next to the structural aspects also the behavioral aspects of real world objects. This paper presents such a method. lt is based on the Behavior lntegrated Entity Relationship Approach which considers the structural as well as the behavioral aspects of the real world objects to be modeled. The structural aspects are represented by different entity sets in an extended entity-relationship diagram. The behavioral aspects are represented by different activities which correspond to transitions in an entity-state/transition diagram. The entity sets in the extendend entity-relationship diagram and the activities in the corresponding entity-state/transition diagram completely characterize the object classes of an object-oriented database. The data structures of the classes are given by the entity sets. The associated operations are determined by the respective activities. The public effects of the operations are defined by the pre- and poststates of the corresponding activities.