Left ventricular circumferential end-diastolic stress (Sed), peak systolic stress (Sps), and compliance at end-diastole ([dV/VdP]ed) were estimated in 13 subjects with normal left ventricles (N group), nine subjects with inappropriate hypertrophy (IH group), five with aortic valvular stenosis (AS group), and six with congestive cardiomyopathy (CC group). The product of Sed and (dV/dP)ed was employed as an index of “muscle fiber stretch” and related to systolic indices of ventricular performance. Compliance was significantly less than normal in IH (P< 0.001), in AS (P< 0.01), and in CC (P< 0.001), while end-diastolic volumes were smaller than normal (P< 0.05), normal (P= NS), and larger than normal (P< 0.001) in the three groups, respectively. Sed was normal in IH and AS but elevated in CC (P< 0.001), while Sps was decreased in IH and normal in AS and CC. “Muscle fiber stretch,” however, was substantially less than normal in IH (P< 0.001), indicating that the low Sps is due at least in part to short sarcomeres. In CC, despite a markedly elevated preload, “muscle fiber stretch” was normal (P= NS), while work indices of the ventricle were diminished indicating depressed ventricular function. Thus, the product of Sed and (dV/VdP) ed provides a normalized index of “muscle fiber stretch,” which permits one to compare length-tension or length-work relationships in diseased ventricles of varying dimensions and compliance.