OBJECTIVE To determine if transitioning patients from a pharmacist- managed anticoagulation clinic after stabilization of warfarin therapy to physician-managed care alters the quality of anticoagulation care. METHODS Retrospective medical record review. METHODS Pharmacist-managed, urban academic medical center-based outpatient anticoagulation clinic. METHODS Forty patients who were stabilized on warfarin therapy. RESULTS Quality of anticoagulation care was measured by percentage of international normalized ratios (INRs) in target range, anticoagulation-related health care visits, and responses to satisfaction surveys. A significant decrease in anticoagulation control was observed on transition to physician-managed care. Before transition, 76% of all INRs were in target range versus 48% after transition (p<0.0001, chi(2) test). When performing paired analysis, a median 75% of each patient's INRs were therapeutic before transition compared with 36.5% after (p<0.0001, Wilcoxon signed rank test). Thirty-two percent of first INR values measured after transition from the clinic were in target range, and the median time to first follow-up INR was 41 days. The number of INR values above 4.5 and below 1.5 increased significantly after transition from the anticoagulation clinic (p<0.0001 and p=0.01, respectively, chi(2) test). Before transition from the anticoagulation clinic, two anticoagulation-related emergency department visits were reported in one patient. After transition, 13 cases of additional medical care were reported among seven patients; seven of the 13 cases required an office visit with the physician, and six resulted in emergency room evaluation. None of these cases resulted in hospitalization. Patient satisfaction with clinical care provided by the anticoagulation clinic was significantly higher before transition. CONCLUSIONS Transition of patients from a pharmacist-managed anticoagulation clinic back to physician-managed anticoagulation care after stabilization of warfarin therapy was associated with a significant decrease in INR control, increased medical care related to anticoagulation, and decreased patient satisfaction.