Cardiac magnetic resonance (MR) imaging with late gadolinium enhancement (LGE) is used to detect and assess the myocardial damage seen with a variety of cardiomyopathies. Gadolinium-based contrast material accumulates in the expanded interstitial space of the myocardium. Areas with LGE correspond to replacement fibrosis, fibrofatty change, epithelioid granuloma, inflammatory cell infiltration, cardiomyocyte necrosis, and amyloid deposition-conditions that represent a focal increase in interstitial space. Areas without LGE correspond to interstitial or plexiform fibrosis, mildly degenerated cardiomyocytes, inflammatory cell infiltration, and diffuse amyloid deposition-conditions that represent diffuse increases in interstitial space. LGE MR imaging cannot depict these diffuse changes and does not enable quantitative evaluation of this increased interstitial space because on inversion-recovery MR images, the inversion time is adjusted to null the signal from normal-appearing or the least enhancing regions of the myocardium. Thus, the absence of LGE does not always indicate normal myocardial tissue. The use of current T1 mapping techniques enables one to overcome these drawbacks of LGE imaging, detect diffuse myocardial abnormalities, and perform quantitative analysis of the interstitial space. The authors describe the histopathologic and corresponding cardiac MR imaging findings of hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, cardiac sarcoidosis, giant cell myocarditis, and cardiac amyloidosis-mainly those seen on LGE MR images-as assessed by using whole-heart specimens obtained from autopsy or transplantation. ©RSNA, 2017.