Recent studies have shown that hypertension is poorly controlled in many populations worldwide. Electrocardiographic left ventricular hypertrophy is a common manifestation of preclinical cardiovascular disease that strongly predicts cardiovascular disease morbidity and mortality. However, little information is available regarding the role of left ventricular hypertrophy in blood pressure (BP) control. We aimed to assess the relationship between electrocardiographic left ventricular hypertrophy and BP control in the China Stroke Primary Prevention Trial. The study population included 17,312 hypertensive patients who were selected from a group of 20,702 adults who had participated in the China Stroke Primary Prevention Trial and had undergone electrocardiography at baseline visit. Multivariate analysis identified left ventricular hypertrophy as a predictor of unsatisfactory BP control. The results revealed that 8.1% of hypertensive adults exhibit left ventricular hypertrophy and that the disease is more prevalent in males (12.8%) than in females. Multivariate regression analysis showed that the electrocardiographic left ventricular hypertrophy group had a significantly higher rate of unsatisfactory BP control [odds ratio (OR) 1.42, 95% confidence interval (95% CI) 1.26-1.61, P < .001) than the nonleft ventricular hypertrophy group.Notable differences in BP control were also observed among males (OR 1.37, 95% CI 1.17-1.60, P < .001) and females (OR 1.45, 95% CI 1.18-1.77, P < .001) and especially among patients with comorbid diabetes (OR 2.32, 95% CI 1.31-4.12, P = .004). In conclusion, the results of this study indicate that electrocardiographic left ventricular hypertrophy appears to be an independent predictive factor for poor BP control, especially in females and patients with comorbid diabetes.