Background: We sought to characterize patient factors and regional variations associated with vitamin K antagonist (VKA) use in patients with heart failure (HF) and atrial fibrillation (AF) in areas outside the United States and Europe. Methods: The ADHERE-International registry enrolled patients with decompensated HF from 10 Asia Pacific and Latin American countries from December 2005 to January 2009. Rates of VKA use in patients with HF and either new-onset AF or a history of AF were determined and compared according to CHADS 2 scores. Multivariable logistic regression and hierarchical modeling with random effects for hospitals were used to determine clinical and regional factors associated with VKA use at discharge. Results: Among 9,706 admissions, there were 2,358 (24.3 ) with prior AF and 674 (6.9 ) with new-onset AF. The median age was 71 years (25th-75th percentiles 59-79) for prior AF and 69 (57-80) for new-onset AF patients. The overall rate of VKA use at discharge was 39.5 . Vitamin K antagonist use at discharge was 36.2 in patients with CHADS 2 scores =2 versus 50.2 in patients with CHADS 2 score equal to 1 (P 75 years old, 34.8 in diabetics, and 44.4 in those with prior stroke/transient ischemic attack. After adjusting for patient characteristics, the highest and lowest rates of anticoagulation were in Australia (65.2 ) and Taiwan (25.1 ). Conclusion: International use of guidelines-recommended anticoagulation in HF patients with AF varies significantly across countries and represents an important opportunity for improving quality of care.