The study's objectives were to investigate nuclear stereology and to determine the level of p62, a protein involved in nuclear transport, in human cardiomyocytes from patients with heart failure due to ischemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM). We studied 23 human hearts: 10 had ICM, 10 had DCM, and three were from control subjects. The size of the nucleus was significantly increased in ICM and DCM hearts compared with those from controls (by 60% and 66%, respectively, P = 03), as was the size of the nucleolus (by 59%, P=.02 and 75%, P = 03, respectively). In addition, the p62 level was significantly increased in both forms of cardiomyopathy compared with controls (ICM 110%, P = 01; and DCM 145%, P = 04). In the ICM group, there were correlations between the p62 level and nuclear size (r = 0.615, P = 05) and between the p62 level and the heterochromatin percentage (r = −0.707; P = 02). In conclusion, cardiomyocytes from hearts affected by ICM and DCM showed changes in nuclear and nucleolar morphology. The p62 level had doubled in both forms of cardiomyopathy and, in ICM hearts, there was a correlation with nuclear changes.