Background: The clinical significance and prevalence of exercise-induced ST elevation (ESTE) in non-ischemic dilated cardiomyopathy (NIDCM) patients are unknown. Methods and Results: We retrospectively examined 12-lead ECGs during cardiopulmonary exercise testing in 360 consecutive NIDCM patients (left ventricular ejection fraction (LVEF) <45%) with narrow QRS. ESTE was defined as ≥1.0 mm ST (J-point) elevation compared with baseline. During long-term follow-up for major cardiac events (death, transplantation, or LV assist device implantation), ESTE was recognized in 50 patients (14%). They had much lower LVEF than patients without ESTE (20±7% vs. 27±7%, respectively, P<0.001), whereas the differences in peak V ̇O2 (P=0.01) and V ̇ E/V ̇CO2 slope (P=0.04) were relatively small. Major cardiac events occurred more frequently in patients with ESTE than in those without ESTE (39% vs. 12% at 48 months). Increased event rates were associated with low peak V ̇O2 (<14 ml · min-1 · kg-1) in patients without ESTE (39% vs. 23%, P<0.05), but not in those with ESTE (50% vs. 62%, NS). Cox multivariate analysis revealed ESTE as the strongest independent prognosticator among exercise parameters (hazard ratio: 2.41 [95% confidence interval 1.03-5.63], P<0.05). Conclusions: A substantial number of NIDCM patients exhibit ESTE, which indicates a poor prognosis. Low peak V ̇ O2 and ESTE may reflect different aspects of the pathophysiological processes that deteriorate heart failure.