Objectives: The purpose of this study was to evaluate ethnic differences in left ventricular (LV) remodeling between highly-trained athletes of African/Afro-Caribbean (black) and Caucasian (white) athletes. Background: The upper limits of left ventricular hypertrophy (LVH) are established in white athletes and aid the differentiation of physiologic LVH from hypertrophic cardiomyopathy (HCM). However, there are few data regarding LV remodeling in black athletes, in whom deaths from HCM are more prevalent. Methods: Between 2003 and 2007, 300 nationally ranked black male athletes (mean age 20.5 years) underwent 12-lead electrocardiogram and 2-dimensional echocardiography. The results were compared with 150 black and white sedentary individuals and 300 highly-trained white male athletes matched for age, size, and sport. Results: Black athletes exhibited greater LV wall thickness and cavity size compared with sedentary black and white individuals. Black athletes had greater LV wall thickness compared with white athletes (11.3 ± 1.6 mm vs. 10 ± 1.5 mm; p < 0.001). In absolute terms, 54 black athletes (18%) had LV wall thickness >12 mm compared with 12 white athletes (4%), and 3% of black athletes exhibited LV wall thickness ≥15 mm compared with none of the white athletes. Black athletes with LVH displayed an enlarged LV cavity and normal diastolic function. Conclusions: Black athletes develop a greater magnitude of LVH compared with white athletes; therefore, extrapolation of conclusions derived from white athletes has the potential of generating false-positive diagnoses of HCM in black athletes.