The research on distributed autonomous robotic systems which has been carried out in RIKEN results in a conclusion that development of new elemental technologies is essential for realization of an collective robot system. In this paper, the required elemental technologies in mechanisms, sensory systems, and communication systems of collective robots are mentioned, and some elemental technologies developed so far are introduced. Interaction between collective robots and their environment is discussed, and an intelligent data carrier system is introduced as an example of a new device for the interaction. Human interface for operating collective robots is also discussed, which enables cooperation between collective robots and a human operator.