['Manual assessment of radial arterial pulse character remains an important determinant of physiological status in military and civilian casualties. This study hypothesized that changes in radial pulse character and mental status (presyncopal symptoms) in humans occur only during the later stages of progressive reductions in central blood volume in close association with systolic blood pressure (SBP).', 'Pulse character (i.e., normal, weak, absent), estimated stroke volume (SV), SBP, and diastolic blood pressure were measured continuously during baseline supine rest and during progressive reductions of central blood volume to cardiovascular collapse with application of lower body negative pressure (LBNP) in 19 healthy human volunteer subjects.', 'LBNP resulted in a progressive reduction in SV. At early stages of LBNP, both radial pulse character and SBP were well-maintained. Although both radial pulse character and SBP decreased with subsequent increases in LBNP, these changes occurred only after an approximate 55% reduction in SV and were associated with the onset of presyncopal symptoms. Changes in mental status did not occur until the point of cardiovascular collapse.'] Are changes in pulse character and mental status late responses to central hypovolemia?