The Development of Attachment and Affiliative Systems was selected as the topic for a three-day workshop held at Estes Park, Colorado, in May, 1980. The papers which resulted from this effort not only reflect a recent intensity of research in this area, but also highlight a mounting need for ask ing questions across disciplines and for integrating theories. The sponsor of the workshop was the Developmental Psychobiology Research Group (DPRG) of the Department of Psychiatry, University of Colorado Medical School, a group which itself is interdisciplinary and which has met regularly since 1969 to criticize research, ask questions, and discuss findings. In 1974, the Group was awarded an endowment fund by the Grant Foundation after a request for a proposal initiated by Philip Sapir and Douglas Bond. The aims of this fund are to facilitate the research of young investigators, to encourage new research, and to provide seed money for collaborative ventures. Much of what is reported here results from that support. Thus, happily, not only are the contributions timely by virtue of converging on an important topic, but they also commemorate more than five years of Grant Foundation support. Once the topic was chosen, a small number of guests were invited to participate. The papers of Timiras, Sackett, Konner, and Lamb represent dif fering perspectives from neurobiology, primatology, cultural anthropology, and social psychology.