The transvenous technique of endomyocardial biopsy was developed over 15 years ago. 1–3 Before the proliferation of heart transplant centers, this procedure was performed at only a limited number of transplant and heart failure centers in the United States. Complication rates for endomyocardial biopsy are quoted in the published reports, but detailed analyses in specific patient populations are lacking. 4–6 One retrospective study has suggested that the procedural risks differ in transplant and nontransplant patient populations. 7 The performance of endomyocardial biopsy to exclude cardiac allograft rejection is an accepted indication in heart transplant recipients. The merit of endomyocardial biopsy in diagnosing myocarditis and evaluating cardiomyopathy has been questioned because the diagnostic sensitivity of the procedure is limited and the results will not significantly influence patient management. 8–11 Therefore, clarification of the risks of this procedure in patients with unexplained heart failure allows clinicians to make informed decisions regarding the risk/ benefit ratio of the procedure in specific patients. This study documents the procedural complications of endomyocardial biopsy in 706 consecutive patients with cardiomyopathy evaluated at a single institution.