Objective: To study the effects of nuclear factor-κB(NF-κB) activation and tumor necrosis factor-α(TNF-α) expression on heart failure after myocardial infarction in rats. Methods: Male Wistar rats were divided into the sham operation(SO) group and myocardial infarction(MI) group. The left anterior descending branch of the left coronary artery of the rats in MI group was ligated with a suture to induce MI. Sham operation was done in those of the SO group. All the rats were killed in the 4th,8th and 12th week after the arterial ligation respectively. The hemodynamic parameters and the wet weight of the right and left ventricles were recorded. The protein expression of TNF-α and the activity of NF-κB of the non-infarcted myocardium were determined with West blot and electrophoretic motility shift assay(EMSA) respectively.Results: Significant lower mean arterial pressure(MAP) and maximal ascending and descending velocity of left ventricular pressure(+dp/dtmax) and significant higher left ventricular end-diastolic pressure(LVEDP) were found in the rats of the MI group than in those of the SO group(P<0.05).Left ventricular relative weight(LVRW) and right ventricular relative weight(RVRW) were higher in the MI group than in the SO group(P<0.05) with an exception that LVRW showed no significant difference between the MI and SO groups in the 12th week after arterial ligation. The expression of TNF-α and the activity of NF-κB were increased in the non-infarcted myocardium after the arterial ligation. Conclusion: Overexpression of TNF-α and significant increase of the activity of NF-κB play an important role in the postinfarctional ventricular remodeling and progression of heart failure.