There are few morphologic studies on idiopathic dilated cardiomyopathy (CM) treated with transplant. We prospectively correlated gross, histologic, and clinical findings pertaining to hearts explanted in a 5-year period from patients with a clinical diagnosis of nonischemic CM and also correlated left ventricular diameter with preoperative echocardiographic reports. Of 64 patients with a clinical diagnosis of dilated cardiomyopathy (DC), 42 were men (age, 51 ± 13 y) and 22 were women (age, 42 ± 18 y). The pathologic diagnosis was idiopathic (dilated) cardiomyopathy (DC) in 55 patients (86%) and features of specific CM in 9 patients (14%). Specific diagnoses were fibrofatty change consistent with arrhythmogenic right ventricular cardiomyopathy (n=6), amyloidosis (n=2), and sarcoidosis (n=1), none of which were suspected clinically. The 55 hearts with idiopathic DC had a mean heart weight of 508 (range, 220 to 980) g. Pathologic subsets of the DC group included 4 hearts without enlargement, cavity dilatation, or significant histologic findings (minimal DC); 3 hearts with histologic evidence of healed myocarditis; and 5 hearts with mildly noncompacted left ventricle with hypertrabeculation. Five patients had prior mitral or tricuspid valve replacement/repairs to manage heart failure. There were 7 postpartum DC cases, 1 with a histologic pattern of healed myocarditis and 1 alcoholism-associated DC. Familial DC comprised 16% (9 of 55) of patients. In patients without prior assist device placement, pathologic left ventricular cavity diameter correlated with echocardiographic end-diastolic volume (r , 0.8, P<0.0001). Morphologically, DC is a heterogeneous group. Areas of fibrofatty change and features of noncompaction are not uncommon. Left ventricular measurement at explant correlates well with echocardiographic findings, with a relatively consistent underestimation of the diameter.