Research concerning the effects of age and fitness on cerebral blood flow velocity during orthostatic stress is limited. Therefore, cardiovascular and cerebral blood flow responses were examined during graded lower body negative pressure (LBNP) in fit (10 young, 10 elderly) and unfit (10 young, 10 elderly) subjects. Subjects aged 60 or over were classified in the elderly group and subjects aged 20-30 were classified in the young group. LBNP Tolerance Index (LTI) did not differ significantly between the groups. The main findings of the study are that 1) cerebral blood flow velocity remains fairly constant during LBNP (compared to rest) until presyncope, 2) cerebral blood flow responses do not significantly differ between the elderly and young, and 3) cerebral blood flow significantly decreases more in fit people than in unfit people at presyncope. In other words, cerebral blood flow decreases more in fit people regardless of age. Our findings suggest that the mean cerebral blood flow velocity remains fairly constant throughout LBNP until presyncope, in which the fit young and fit elderly groups had significant decreases in cerebral blood flow compared to rest.