Alterations in cortical activation processes due to chronic low blood pressure were investigated. In 40 hypotensive subjects and 40 normotensive controls, the contingent negative variation (CNV), induced by a constant foreperiod reaction time task, was assessed at nine scalp sites (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). Additionally, spontaneous EEG was recorded at resting conditions. In hypotensives, a reduced amplitude of both the early and the late component of the CNV were found at Cz. At Fz the early CNV was reduced. Hypotensives exhibited longer reaction times, and the reaction time was negatively correlated with the CNV amplitude. Resting alpha power correlated negatively with blood pressure. The findings can be related to cognitive deficits due to hypotension found in earlier studies. The effects of hypotension on cortical activity are discussed to be mediated by afferents from the cardiovascular system to the prefrontal cortex as well as by reduced cerebral blood flow.