We evaluated the influence of dementia severity on cognitive performance in two groups of individuals with vascular dementia (VaD). Performance on the Mini-Mental State Exam (MMSE) was used to determine dementia severity. Tests of executive function, psychomotor speed, memory, language, and visuospatial function were administered. As expected, individuals with severe VaD (MMSE < 18) performed significantly more poorly than individuals with mild VaD (MMSE > or = 18) on most tests. More important, deficits were evident for both groups in each cognitive domain when compared to normative data. These results indicate that multiple cognitive domains are affected even in mild cases of VaD. Clinicians should be aware that although the presence of "patchy" cognitive deficits may indicate stroke, general cognitive dysfunction may occur in mild cases of VaD.