Left ventricular hypertrophy (LVH), defined as an abnormal increase in left ventricular mass (LVM), is detected by echocardiography in 16-19% of a general population. Its prevalence is strongly associated with age, systolic blood pressure and obesity. In addition to the assessment of LVM, echocardiography allows different forms of left ventricular remodelling in hypertension to be described: eccentric or concentric, and symmetric or asymmetric LVH. The significance of the different forms, however, is not yet well defined. Increased LVM is now recognized as a powerful, independent risk factor for all cardiovascular diseases. This observation is at variance with the general concept that LVH is a useful adaptation of the left ventricle to chronic overload. To explain this paradox, three hypotheses are proposed: LVH serves as a marker, a limited adaptative process, or a pathological process. Each hypothesis implies different therapeutic approaches; thus it is necessary to clarify the reasons why LVH is such an important risk factor.