The idea ofteamwork in health care emerged at several times during the th 20 centuryas the resultofshifts in the nature and demandsofhealth care and societal needs. Examples include medical and surgical teams serving the military in World War II, primary care teams staffing Community Health Centers created by President Johnson's War On Poverty, and geriatric care teams established to serve the rapidly growing number of aging citizens. Collaborative teamwork surfaced as a rational solution to health care needs, but political and economic consensus to support widespread implementation was lacking. The increasing complexity ofproviding health care seemed best served by the skills and efforts of interdisciplinary teams, but such care was viewed as expensive so e.valuation ofits effectiveness became essential. There were major problems in conducting such evaluation, however. First, no clear theory guided the concept and practice of teamwork. Early attempts to employ theoretical constructs explaining the behavioral and organizational phenomena of teamwork borrowed from theories of group dynamics, communication, organizational development, and general systems. Further, few reliable, validated instruments existed to evaluate team process, function, or effectiveness. The best early efforts at research and evaluation came from academic centers funded by the Office of Interdisciplinary Programs of the Bureau of Health Professions (1975-78) and from the Veterans Affairs' Interprofessional Team Training & Development Program.