Objectives: Left ventricular hypertrophy and albuminuria have both been shown to predict increased cardiovascular morbidity and mortality. However, the relationship between these markers of cardiac and renal glomerular damage has not been evaluated in a large hypertensive population with target organ damage. The present study was undertaken to determine whether albuminuria is associated with persistent electrocardiographic (ECG) left ventricular hypertrophy, independent of established risk factors for cardiac hypertrophy, in a large hypertensive population with left ventricular hypertrophy who were free of overt renal failure. Methods: Patients with stage II-III hypertension were enrolled in the study if they had left ventricular hypertrophy on a screening ECG by Cornell voltage-duration product and/or Sokolow-Lyon voltage criteria, and clinic blood pressures between 160 and 200/95-115 mmHg and plasma creatinine < 160 mmol/l. A second ECG and morning spot urine were obtained after 14 days of placebo treatment. Renal glomerular permeability was evaluated by urine albumin/creatinine (UACR, mg/mmol). Microalbuminuria was present if UACR > 3.5 mg/mmol and macroalbuminuria if UACR > 35 mg/mmol. Results: The mean age of the 8029 patients was 66 years, 54% were women. Microalbuminuria was found in 23% and macroalbuminuria in 4% of patients. Microalbuminuria was more prevalent in patients of African American (35%), Hispanic (37%) and Asian (36%) ethnicity, heavy smokers (32%), diabetics (36%) and in patients with ECG left ventricular hypertrophy by both ECG-criteria (29%). Urine albumin/creatinine was positively related to Sokolow-Lyon voltage criteria and Cornell voltage-duration product criteria. In multiple regression analysis, higher UACR was independently associated with older age, diabetes, higher blood pressure, serum creatinine, smoking and left ventricular hypertrophy. Patients smoking > 20 cigarettes/day had a 1.6-fold higher prevalence of microalbuminuria and a 3.7-fold higher prevalence of macroalbuminuria than never-smokers. ECG left ventricular hypertrophy by Cornell voltage-duration product or Sokolow-Lyon criteria was associated with a 1.6-fold increased prevalence of microalbuminuria and a 2.6-fold increase risk of macroalbuminuria compared to no left ventricular hypertrophy on the second ECG. Conclusions: In patients with moderately severe hypertension, left ventricular hypertrophy on two consecutive ECGs is associated with increased prevalences of micro- and macroalbuminuria compared to patients without persistent ECG left ventricular hypertrophy. High albumin excretion was related to left ventricular hypertrophy independent of age, blood pressure, diabetes, race, serum creatinine or smoking, suggesting parallel cardiac damage and albuminuria.