No uniform criteria currently exist for rating white-matter (WM) high-signal foci on MRI. Ratings are based on descriptive terms, different pulse sequences and different WM areas. Reports on the prevalence and clinical correlates of high-signal foci have been contradictory. We wanted to examine the contribution of the pulse sequence and WM area on rating WM changes. We analysed WM changes separately on T2-, protondensity (PD)- and T1-weighted images in periventricular, subcortical, watershed area and deep WM. The difference between T2- and PD-weighted images was significant for frontal caps, counting small foci or analysing subcortical changes. T1-weighted images showed significantly less change, but the number of foci detected was greater than previously thought. The prevalence of WM high-signal foci was greatest in the watershed zone and smallest in the subcortical area. There was a significant correlation between foci in different areas.