Collaborative teamwork is viewed by many as a characteristic of effective working relationships between adults who provide special education and related services in educational settings. Although a substantial body of research exists on the philosophy and practice of collaborative teamwork, the contributions of veteran team members regarding which elements of this knowledge base they view as essential has been largely absent. The purpose of the present study was to obtain the opinions of practicing team members regarding those elements of teamwork they found essential, as well as those they view as non-essential, to their professional practice. The responses of 46 team members (17 special educators, 9 occupational and physical therapists, and 20 speech and language pathologists), were obtained through their completion of a questionnaire. The questionnaire was organized according to three professional practice themes of teamwork: 1) the philosophy of collaborative teamwork; 2) collaborative team structures; and 3) collaborative team functions. Team members indicated which elements within each professional practice theme they viewed as essential to the knowledge base for service on collaborative educational teams. Responses were variable within and across the three themes with the strongest support expressed for the process of collaborative problem solving. The implications of these data for the practice of collaborative teamwork in contemporary public schools are explored. (Contains 5 tables.)