Abstract--The electrocardiographic strain pattern is a marker of left ventricular hypertrophy and adverse cardiovascular prognosis. The objective of this study was to assess the factors associated with the presence of ECG strain in patients with resistant hypertension and, specifically, to evaluate the relationships between strain and left ventricular mass (LVM) and structure. In a cross-sectional design, 440 resistant hypertensive subjects were evaluated. Clinical, laboratory, electrocardiographic, 24-hour ambulatory blood pressures, and echocardiographic variables were obtained. Statistical analysis involved bivariate tests, analysis of covariance, and multivariate logistic regression. An ECG strain pattern was present in 101 patients (23%). Patients with strain were more frequently men with lower body mass index, had more target-organ damage, higher 24-hour blood pressure, higher serum creatinine and 24-hour microalbuminuria, and more prolonged QT interval duration than those without strain. After controlling for all covariates, the presence of strain remained associated with increased LVM and wall thicknesses, both in all patients and also in those with echocardiographic left ventricular hypertrophy. Furthermore, the presence of ECG strain was associated with increased LVM (P<0.001), higher 24-hour systolic blood pressure (P<0.001), prolonged maximum QTc-interval duration (P<0.001), lower waist circumference (P=0.009), male gender (P=0.011), physical inactivity (P=0.020), higher serum creatinine (P=0.031) and fasting glycemia (P=0.027), and the presence of coronary heart disease (P=0.001) and peripheral arterial disease (P=0.045). Thus, in resistant hypertension patients, the presence of ECG strain is independently associated with increased left ventricular wall thicknesses and mass and also with other potentially adverse factors. These relationships offer insight into the known association between strain and unfavorable cardiovascular prognosis.