This paper presents a general architecture and a platform developed to implement distributed applications as a set of cooperating intelligent agents. It also shows how this architecture has been used to implement a distributed control system for a complex process: the economic control of a fossil-fuel fired power plant. Agents in this application encapsulate different distributed hardware/ software entities: neural and fuzzy controllers, a data-acquisition system, presentation manager, etc. These agents are defined in ADL (Agent Description Language), a high-level specification language, and interchange data/knowledge through service requests using a common knowledge-representation language.