A theoretical framework for designing interfaces for complex human-machine systems is proposed. The framework, called ecological interface design (EID), is based on the skills, rules, knowledge taxonomy of cognitive control. The basic goal of EID is twofold: first, not to force processing to a higher level than the demands of the task require, and second, to support each of the three levels of cognitive control. Thus, an EID interface should not contribute to the difficulty of the task, and at the same time, it should support the entire range of activities that operators will be faced with. Three prescriptive design principles are suggested to achieve this objective, each directed at supporting a particular level of cognitive control. Theoretical foundations of the framework are laid out. Particular attention is paid to presenting a coherent deductive argument justifying the principles of EID. In addition, three sources of converging support for the framework are presented. First, a review of the relevant psychological and cognitive engineering literature reveals that there is a considerable amount of research that is consistent with the principles of EID. Second, an examination of other approaches to interface design indicates that EID has a unique and significant contribution to make. Third, the results of an initial empirical evaluation also provide some preliminary support for the EID framework. Some issues for future research are outlined.