A theoretical framework for designing interfaces for complex systems is de-scribed. The framework, called ecological interface design (EID), suggests a set of principles for designing interfaces in a way that supports the funda-mental properties of human cognition. The basis of EID is the skills, rules, knowledge model of cognitive control. In order to support the full range of operator problem solving activities, EID suggests how to design interfaces that simultaneously support each of the three levels of cognitive control, but that do not force processing to a higher level than the demands of the task require. The EID approach extends the concept of direct manipulation inter-faces by taking into account the added complications introduced by complex systems. In this paper, we describe the development of the framework, its theoretical foundations, and examples of its application to various work domains.