Here we describe a correlative study of cerebral blood flow (CBF) using global, local CBF and carotid flow measurements. The primary objective of this study was to establish a relationship between REG and CBF autoregulation. Rheoencephalography (REG), a rarely used method to measure CBF, is a potential tool of non-invasive continuous life sign monitoring and detection of early cerebrovascular alteration. However, the anatomical background of REG is not clearly understood. Two experimental studies were undertaken on anesthetized rats to define two CBF measurements: (1) CO₂ inhalation, and, (2) clamping of common carotid arteries. Measurement of CBF was taken with REG, laser Doppler flowmetry (LDF) and carotid flow by Doppler ultrasound. Data were off-line processed. During CO₂ inhalation, the increases in REG and LDF were significant (p = 0.0001), while carotid flow and systemic arterial pressure decreased. During carotid artery clamping, the decrease in REG and Doppler ultrasound was significant (p = 0.0001). REG showed cerebrovascular reactivity, indicating the relationship to arteriolar changes. Compared to LDF and carotid flow, only REG showed the classical CBF autoregulation.