The rate and extent of progression of white matter hyperintensities (WMH) over time in elderly subjects is yet unclear. These abnormalities may represent an early form of subcortical vascular dementia. As to whether such changes could be used, as a surrogate marker for this subtype of vascular dementia remains to be determined. So far there exists only a very limited number of studies determining the rate, clinical predictors and cognitive consequences of WMH evolution. There is evidence that these changes do progress over time, however the results of the different studies cannot be compared due to methodological differences. The Austrian Stroke Prevention Study reported that 17.9% of normal individuals show progression over time. The only published quantitative data demonstrated an absolute increase of 1.1 cm(3) over an observational period of 4 years in healthy subjects. Diastolic blood pressure, early confluent or confluent WMH at baseline and genetic variants in the angiotensinogen gene are so far the only known predictors of WMH progression. The Austrian Stroke Prevention Study did not find an association between the evolution of WMH and cognitive functioning but the statistical power of this analysis was small and the relationship needs to be further explored.