Abstract—Although men and women differ in the magnitude of ECG left ventricular hypertrophy, whether gender differences exist in the degree of regression of ECG left ventricular hypertrophy during antihypertensive therapy is unclear. ECG left ventricular hypertrophy defined using gender-adjusted Cornell product and Sokolow-Lyon voltage criteria was assessed serially in 9193 hypertensive patients treated with losartan- or atenolol-based regimens. Changes in ECG left ventricular hypertrophy were measured from baseline to last in-study visit, and above-average regression of hypertrophy was identified by a 236-mm · ms reduction in Cornell product or 3.5-mm reduction in Sokolow-Lyon voltage. During mean follow-up of 4.8±0.9 years, women had less reduction in Cornell product (-149±823 versus -251±890 mm · ms) and Sokolow-Lyon voltage (-3.0±6.8 versus -4.8±7.7 mm) than men (both P<0.001). After adjusting for baseline ECG left ventricular hypertrophy levels, baseline and change in systolic and diastolic pressures, treatment group, age, and other baseline gender differences, women had significantly less reduction in both Cornell product (adjusted means: -137 versus -276 mm · ms; P<0.001) and Sokolow-Lyon voltage (-3.6 versus -4.1 mm; P=0.005) than men and were 32% less likely to have had greater than the median level of regression of Cornell product left ventricular hypertrophy (95% CI: 24% to 39%; P<0.001) and 15% less likely to have had regression of left ventricular hypertrophy by Sokolow-Lyon criteria (95% CI: 5% to 23%; P=0.003). Thus, women have less regression of ECG left ventricular hypertrophy than men in response to antihypertensive therapy, independent of baseline gender differences in the severity of ECG left ventricular hypertrophy and after taking into account treatment effects and blood pressure changes.