In Health Services Research, Hummy Song and colleagues develop and validate a survey instrument designed to measure team dynamics in primary care. The authors study 1,080 physician and non-physician health care professionals at 18 primary care practices participating in a learning collaborative to improve team-based care. They administer a cross-sectional survey addressing team dynamics, and assessed reliability and discriminant validity of survey factors, as well as the overall survey’s goodness-of-fit. They find that this model demonstrated adequate fit, scale reliability, and discriminant validity. Survey results suggest that conditions for team effectiveness, shared understanding, and supportive processes are associated with acting and feeling like a team, and in turn, perceived team effectiveness. The authors conclude that is possible to reliably measure primary care team dynamics using this survey, and that it may be used in ambulatory settings to study teamwork and explore the effect of efforts to improve team-based care.