The purpose of this study was to identify features of successful collaboration among professionals and parents involved in supporting children with disabilities in early childhood education and care. The study employed a multiple-case study design comprising 6 cases and 30 adult participants, who were interviewed regarding their collaboration on behalf of 6 children with significant disabilities ranging in age from 3 to 5 years. Applying a system-theoretical approach, analysis led to the development of a framework based on the concepts of 'internal' and 'external' features of collaboration. Whereas internal aspects refer primarily to the interpersonal interactions of parents and professionals, external features are linked to conditions that occur at a greater 'distance' from these interactions, yet nonetheless appear to have a substantial impact on participants' beliefs about whether the collaboration is successful. We argue that external influences have too often been overlooked in the literature on multidisciplinary collaboration in this context. (author abstract)