<p>[Background] Autophagy is a self-degradation system of intracellular organelles and found in failing heart. We investigated whether angiotensin II (ANG II) enhanced myocyte autophagy and the role of autophagy in ANG II-induced injury. [Methods and Results] Neonatal rat cardiac myocytes were treated with ANG II (1–100 nmol/L). ANG II dose dependently increased autophagy, assessed by microtubule-associated protein 1 light chain (LC) 3-II expression. It also enhanced the intracellular reactive oxygen species (ROS), detected by H2DCFDA staining. NADPH oxidase- and mitochondria-derived ROS production was increased by ANG II, while ANG II-induced autophagy was suppressed by inhibitors of these sources of ROS. ROS-producing mitochondria colocalized with lysosomes after ANG II stimulation. Myocyte apoptosis was observed using nuclear staining with DAPI. A 6-hour stimulation with ANG II did not affect myocyte apoptosis, while a co-treatment with 3-methyl-adenine (3MA), an autophagy inhibitor, increased apoptosis. A longer ANG II stimulation for 24 hours induced apoptosis, while the co-treatment with 3MA did not lead to further increase. [Conclusion] ANG II enhanced intracellular ROS production, leading to autophagy in myocytes. Autophagy was beneficial because it removed damaged mitochondria, which suppressed myocyte apoptosis in the early stages of the ANG II stimulation, while the longer ANG II stimulation itself induced apoptosis that was not effectively suppressed by autophagy.</p>