The effects of compression rate on carotid blood flow were investigated in awake rats submitted to hyperbaric experiments conducted up to 70 bar (7 MPa, gauge pressure) with either slow compression (0.1 bar/min), i.e., inducing only mild High Pressure Neurological Syndrome (HPNS), or fast compression (2 bar/min), i.e., in the earlier time course of experiments leading to epileptic seizures. Implanted transit-time ultrasonic flowprobes were used, and data were analyzed by regression methods. Mean carotid blood flow increased with ambient pressure during either low or high compression rate, but the increase was significantly more important with the latter. These results evidenced that carotid blood flow increased with ambient pressure, and moreover that this enhancement depends on compression rate.