A body of evidence indicates that masked hypertension is a significant predictor of cardiovascular disease, but how to identify these patients is still a matter of dispute. Data obtained in several cross-sectional studies have demonstrated that masked hypertension is associated with increased left ventricular mass index and carotid intima-media thickness, and impaired large artery distensibility. Furthermore, in longitudinal studies, masked hypertension was a strong predictor of cardiovascular morbidity and mortality. Several factors that can selectively raise ambulatory blood pressure increase the likelihood of having masked hypertension. These include younger age, smoking, alcohol use, contraceptive use in women, sedentary habits and central obesity. In addition, masked hypertension is more common in individuals with high-normal clinic blood pressure or transiently elevated blood pressure. Increased reactivity to daily life stressors and behavioural factors are other important predictors of masked hypertension. In clinical practice, masked hypertension should be searched for in individuals who are more likely to have this condition or are at increased risk of cardiovascular events including those with coronary, cerebrovascular or kidney disease, patients with diabetes and individuals with a high cardiovascular risk profile. To determine whether the use of ambulatory blood pressure monitoring is cost-effective in these individuals, further research is needed. Blood Press Monit 10:307-310 (c) 2005 Lippincott Williams & Wilkins.