Engineering methodology was used to develop a mathematical model of the cardiovascular system which is capable of predicting the effects of acceleration stress on peripheral and central vision. The basic model, previously reported, has been extended to include a simulation of the venous system and a number of additional refinements. It includes simulations of the heart, arterial, and venous system, physiologic compensatory mechanisms, and the effects of protective devices and maneuvers. Information derived from the model is important to understanding of cardiovascular responses to acceleration stress, mechanisms which determine tolerance, and factors which limit a pilot's performance. The model has been used to study the relative effectiveness of several acceleration protection methods and devices, including an anti-G suit design. Results from simulations using the model correlate well with reports in the literature.>