After presenting with new onset idiopathic dilated cardiomyopathy, one third of patients experience dramatic recovery of left ventricular function, while for the majority chronic heart failure and left ventricular dysfunction persist. This marked variation in clinical outcomes is determined in part by genetic heterogeneity of the systemic response to myocardial injury. This population has been excluded from most clinical trials and few studies have examined the role of cytokine and neurohormonal mediators in modulating the balance between left ventricular recovery and remodeling in early cardiomyopathy. This proposal will investigate whether genetic polymorphisms of inflammatory and neurohormonal mediators influence subsequent clinical outcomes for patients with recent onset primary (idiopathic) dilated cardiomyopathy. The study will enroll 500 patients with recent onset left ventricular dysfunction (LVEF < 0.40) due to non-ischemic primary cardiomyopathy at eleven centers and follow these patients prospectively to evaluate subsequent left ventricular recovery and freedom from clinical events.