OBJECTIVES: The aim of this study was to describe hospital variation and factors associated with adherence to guidelines for implantable cardioverter-defibrillator (ICD) therapy. BACKGROUND: Studies have shown incomplete application of ICD therapy in eligible heart failure (HF) patients. METHODS: New or discharge prescription rates for ICD therapy (ejection fraction or= 0.05) were similar across ICD, whereas higher ICD-rate hospitals had higher adherence to GWTG-HF performance measures (beta-blocker use, evidence-based beta-blocker use, aldosterone-antagonist, hydralazine/nitrate; p < 0.05) except warfarin in patients with atrial fibrillation (p = 0.18). CONCLUSIONS: There is significant unexplained hospital variation in the use of ICD therapy among potentially eligible HF patients. However, hospitals that use ICD therapy more often also have more rapidly adopted other newer evidence-based HF therapies.