Left ventricular (LV) hypertrophy has been repeatedly shown to be associated with a marked increase in mortality risk. Available data, however, do not provide evidence that the risk associated with the increase in cardiac muscle mass is independent of the severity of preexistent coronary artery disease. In a cohort of predominantly black patients with a high prevalence of hypertension and LV hypertrophy, LV mass as estimated by echocardiography was found to be a powerful prognostic factor independent of ejection fraction and obstructive coronary disease. After excluding patients with either a dilated LV cavity (diastolic internal diameter greater than 5.8 cm) or asymmetric septal hypertrophy (septal:posterior wall ratio greater than 1.5) LV mass/height remained significantly increased in decedents compared to survivors (116 +/- 38 vs 131 +/- 47 g/m, p = 0.014), while the thickness of the ventricular septum and the posterior wall were even more highly predictive of a fatal outcome (p = 0.003 and 0.001, respectively). After exclusion of patients with eccentric LV hypertrophy, differences in LV muscle mass in survivors and decedents were due entirely to increased thickness of the ventricular wall, and no differences in cavity dimensions or LV ejection fraction were noted. Stepwise regression analysis was used to demonstrate that measures of LV hypertrophy were the most important predictors of survival and eliminated the contribution of all other prognostic factors to the model except the number of stenotic vessels. The relative risk associated with a 100-g increase in mass was 2.1, while a 0.1-cm increase in posterior wall thickness was associated with approximately a 7-fold increase in the risk of dying.(ABSTRACT TRUNCATED AT 250 WORDS)