Study objective: We analyzed 980 emergency department visits for 951 patients with managed care insurance to document gatekeeping interactions and compare ED coding with professional fee billing reimbursements. Methods: A prospective cohort study was performed at 12 academic and community hospital EDs in 4 states involving consecutive ED patients with managed care insurance. The main outcomes measured were gatekeeper decisions, coding levels, and reimbursement. Results: Preauthorization for payment was required from managed care gatekeepers for 876 (89%) patients. Authorization was granted for 490 (56%) of these visits and denied in 176 (20%) visits; gatekeepers were not available for 210 (24%) visits. Reimbursement was initially denied for 211 (43%) of the ED visits preapproved by managed care gatekeepers. Reimbursement was initially denied for most (634 or 65%) visits, and downcoding occurred in the other 346 (35%) visits. Appeals for 560 (57%) visits resulted in a decrease in the number of unreimbursed ED visits to 193 and an increase in the number of reimbursed ED visits to 787. Conclusion: Preauthorization gatekeeping is not predictive of whether managed care third-party payers will initially reimburse ED visits. Overall, almost two thirds of all ED claims were initially denied, and reimbursed claims were uniformly down-coded. On appeal, reimbursement was often reinstated or increased, although billing services only appealed about half of ED visits.