With the rapid progress of information technology, the work environments that cognitive ergonomics (CE) should be concerned with are vastly changing. Among the most important ongoing changes is the appearance of large-scale logical systems. Logical systems are in nature software-based but now grow to be both large-scaled and dynamic, integrating a variety of physical facilities and social mechanisms. The domains include telecommunication and traffic, e-commerce, production control, knowledge management, scheduling and distribution. This paper considers the characteristics of the emerging large-scale logical systems (LLS’s) and discusses the ensuing needs that CE has to prepare to meet. The evasive concept of interaction is emphasized as a potential main theme in the design and evaluation of LLS’s. The directions of further development of CE in the light of this theme are probed. Lastly, it is pointed that the knowledge society brings to the attention of CE the notion of cognitive organization, which increases the complexity in the human part.