In the present study, the authors investigated the relationship between low blood pressure (BP) and attentional performance through the application of a multidimensional diagnostic approach. The authors compared 40 subjects with essential hypotension (mean systolic BP = 97.6 mmHg) with 40 normotensive controls (mean systolic BP = 124.1 mmHg) using 6 computer-based tasks measuring tonic and phasic alertness; selective, divided, and sustained attention; and working memory. To control for possible confounders, the authors used a test battery examining motor performance and a mood questionnaire. BP was monitored continuously during the entire experiment. Hypotensives showed prolonged execution times in each of the attentional tasks (p less than 0.001). Moderately decreased accuracy was found in the tests assessing sustained attention (p = 0.059) and working memory (p = 0.012). Moreover, hypotensives showed smaller elevations in BP during the execution of the cognitive tasks. This study is the first to demonstrate the relationship between BP and cognitive performance while controlling for motor function and mood. (Contains 3 tables, 2 figures, and 2 notes.)