Mounting evidence indicates that social support is associated with better outcomes of cardiovascular disease and reduced all-cause mortality. Much less is known about the specific contribution of marital functioning to these outcomes, and the potential prognostic significance of marital quality for congestive heart failure (CHF) has not been explored. Interview and observational measures of marital quality obtained from 189 patients with CHF (139 men and 50 women) and their spouses were examined as predictors of patient survival up to 48 months after assessment and compared with prediction based on illness severity (New York Heart Association [NYHA] class). Four-year survival rates were 52.5% and 68% for male patients and female patients, respectively. In Cox regression analyses, a composite measure of marital quality predicted 4-year survival as well as the patient's concurrent NYHA class did (both p <0.001). Adjusting for CHF severity did not diminish the prognostic significance of marital functioning, and prediction of survival from marital quality appeared stronger for female than for male patients. Thus, when marital quality and NYHA class are considered jointly, they both make independent, statistically significant contributions to the prediction of patient mortality.