The goal of this study was to examine the frequency of mitral regurgitation (MR) in patients with left ventricular (LV) systolic dysfunction and to relate its presence and severity to long-term survival. Remodeling of the left ventricle after myocyte injury leads to a progressive change in LV size and shape, and it may lead to the development of MR. The frequency of MR and its relation to survival in patients with LV systolic dysfunction has not been completely characterized. We analyzed the histories, coronary anatomy, and degree of MR in patients with symptomatic heart failure and LV ejection fraction <40% who underwent cardiac catheterization between 1986 and 2000. Cox's proportional hazards modeling was used to assess the independent effect of MR on survival. Two thousand fifty-seven patients met study criteria; MR was common in this cohort (56.2%). Of patients with MR, 811 (70.1%) had mild (grades 1+ or 2+) and 345 (29.8%) had moderate or severe (grades 3+ or 4+) regurgitation. Survival rates at 1, 3, and 5 years were significantly lower in patients with moderate to severe MR versus those with mild or no MR (p <0.001). MR was found to be an independent predictor of mortality after multivariable analysis (hazards ratio 1.23, 95% confidence interval 1.13 to 1.34, p = 0.0001). This relation of MR and survival was present in those with ischemic and nonischemic cardiomyopathies. MR is common in patients with LV systolic dysfunction and heart failure. After adjusting for other clinical variables, the presence of MR independently predicted worsened survival.