Background: Assessment of antihypertensive treatment is normally based on the mean value of a number of blood pressure (BP) measurements. However, it is uncertain whether high in-treatment visit-to-visit BP variability may be harmful in hypertensive patients with left ventricular hypertrophy (LVH). Methods: In 8505 patients randomized to losartan vs. atenolol-based treatment in the LIFE study, we tested whether BP variability assessed as SD and range for BP6-24months measured at 6, 12, 18 and 24 months of treatment was associated with target organ damage (TOD) defined by LVH on ECG and urine albumin/creatinine ratio at 24 months, and predicted the composite endpoint (CEP) of cardiovascular death, nonfatal myocardial infarction (MI) or stroke occurring after 24 months (CEP=630 events). Results: In multiple regression models adjusted for mean BP6-24months and treatment allocation, neither high BP6-24months SD nor wide range were related to TOD at 24 months, except for a weak association between Sokolow-Lyon voltage and DBP6-24months SD and range (both b=0.04, P<0.01). Independently of mean BP6-24months, treatment allocation, TOD and baseline characteristics in Cox regression models, CEP after 24 months was associated with DBP6-24months SD [hazard ratio per 1mmHg increase1.04, 95% confidence interval (95% CI) 1.01-1.06, P=0.005], range (hazard ratio 1.02, 95% CI 1.01-1.03, P=0.004), SBP6-24months SD (hazard ratio 1.01, 95% CI 0.99-1.02, P=0.07) and range (hazard ratio 1.006, 95% CI 1.001-1.01, P=0.04). Adjusted for the same factors, stroke was associated with DBP6-24months SD (hazard ratio 1.06, 95% CI 1.02-1.10, P=0.001), range (hazard ratio 1.03, 95% CI 1.01-1.04, P=0.001), SBP6-24months SD (hazard ratio 1.02, 95% CI 1.002-1.04, P=0.04) and range (hazard ratio 1.008, 95% CI 1.001-1.02, P=0.05), but MI was not. Conclusion: In LIFE patients, higher in-treatment BP6-24months variability was independently of mean BP6-24months associated with later CEP and stroke, but not with MI or TOD after 24 months.