In order to more decisively determine if elevated ROS contributed to mtCaMKII cardiomyopathy, we took an orthogonal approach, and interbred mtCaMKII mice with mice transgenically overexpressing a mitochondrial-targeted form of catalase (mCat), an enzyme that decomposes H2O2 into H2O and O2. The gene discussed is MCAT; the disease is cardiomyopathy.