Objectives: To examine a possible relationship between baseline albuminuria and effect of losartan versus atenolol on cardiovascular (CV) events in hypertensive patients with left ventricular hypertrophy, the effect of losartan versus atenolol on albuminuria, and whether the benefits of losartan versus atenolol could be explained by influence of losartan on albuminuria. Design: Double-blind, randomized, controlled trial of 4.8 years. Setting: Out-patient setting. Patients: A total of 8206 with hypertension and left ventricular hypertrophy. Interventions: Losartan or atenolol, supplemented with diuretics and/or calcium antagonists to reach blood pressure < 140/90 mmHg Main outcome measures: The urine albumin/creatinine ratio, and the primary composite endpoint (CEP) of CV death, myocardial infarction, and stroke. Results: The blood pressure was reduced similarly on losartan (30.2/16.6 mmHg) versus atenolol (29.1/ 16.8 mmHg). The risk of a primary CEP increased linearly from the lowest to the highest decile of baseline albuminuria. The benefits of losartan versus atenolol for the primary CEP and for stroke tended to be more pronounced among patients above the median value for baseline albuminuria (urine albumin/creatinine ratio, 1.28 mg/mmol). The decrease in albuminuria was significantly greater with losartan versus atenolol throughout the study (a fifth of the difference in favor of losartan on the primary CEP was explained by the greater reduction in albuminuria on losartan. Conclusions: Baseline albuminuria is a powerful risk factor for CV events. Baseline albuminuria did not identify the group of patients with greatest benefit on losartan versus atenolol in LIFE. Reduction in albuminuria explained one-fifth of the benefits of losartan versus atenolol. © 2004 Lippincott Williams & Wilkins.