To evaluate the clinical significance of ECG depolarization abnormalities of left ventricular hypertrophy, ECG findings were related to echocardiographic or autopsy left ventricular mass, geometry and function as well as hemodynamic overload, in a heterogeneous population of 161 patients. ST depression and asymmetric T wave inversion were present in 21/107 patients not receiving digitalis (19%) and in 33/54 (61%) receiving digitalis. In patients not receiving digitalis their prevalence increased linearly from 0% (0/31) with LV mass less than or equal to 100 grams to 100% (8/8) with LV mass over 400 grams (p less than 0.001). Patients taking digitalis manifested "strain" commonly despite a normal LV mass (4/14, 28%), but even more frequently with an LV mass over 200 grams (27/40, 68%) (p less than 0.05). In the absence of digitalis, repolarization abnormalities were also significantly associated with a reduced ejection fraction (8/17 or 47% versus 8/83 or 10%; p less than 0.001), increased LV internal diameter (9/18 or 50% versus 12/89 or 13%; p less than 0.01), and systolic blood pressure over 140 mm Hg (9/29 or 31% versus 7/61 or 11%; p less than 0.05). Increased thickness of the LV wall was not significantly associated with LV "strain" (p = 0.1). In this population, LV "strain" alone performed as well as other single or combined ECG criteria in the recognition of LVH (sensitivity 52%, specificity 95%). Thus, in the absence of digitalis, repolarization abnormalities are a highly useful ECG sign of LVH, despite numerous other factors capable of causing indistinguishable abnormalities.