BACKGROUND AND AIMS: Increased body mass index (BMI) has been associated with increased cardiovascular morbidity and mortality in hypertension. Less is known about the impact of BMI on improvement in left ventricular (LV) structure and function during antihypertensive treatment. METHODS AND RESULTS: Annual BMI, echocardiograms and cardiovascular events were recorded in 875 hypertensive patients with LV hypertrophy during 4.8 years randomized treatment in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) echocardiography substudy. Patients were grouped by baseline BMI into normal (n = 282), overweight (n = 405), obese (n = 150) and severely obese groups (n = 38) (BMI =24.9, 25.0-29.9, 30.0-34.9, and =35.0 kg/m(2), respectively). At study end, residual LV hypertrophy was present in 54% of obese and 79% of severely obese patients compared to 31% of normal weight patients (both p