Summary: Realizing application systems that match people’s expectations and providing adequate network services for various users under various network and platform environments are difficult challenges. To overcome these problems, we have studied application systems based on multiagent systems and design models of multiagent systems. We propose a method to observe and control the behavioral characteristics of multiagent systems to support the design, development, and operation of such systems. More specifically, we propose a Flexible Distributed System and a Behavioral Characteristics Model, and we apply these two models to the design of an actual multimedia communication system and evaluate the effectiveness of the proposed scheme.