Acute massive hemorrhage in rats is accompanied by consistent changes in the morphofunctional characteristics of erythrocytes: diameter, area, polarization, form factor, and integral and specific optical density. Thus, young initially intact rats showed significant increases in the mean diameter, area, and integral optical density at particular time points after hemorrhage, along with increases in erythrocyte polarization and form factor. Vagotomized rats of the same age group responded to hemorrhage only with an increase in the form factor. Initially intact aged rats in these conditions showed increases in the integral optical density and form factor. Aged vagotomized rats showed increases in erythrocyte mean diameter and area. The nature and dynamics of responses to hemorrhage in initially intact and vagotomized (14 days post-operative) animals were significantly different and had age-dependent features. Thus, the most marked changes in young initially intact animals were seen 3-10 h after hemorrhage, while maximum changes were seen at 3 and 96 h in vagotomized animals of the same age. In aged initially intact rats, the greatest changes in study parameters were seen at 3 and 96 h, while the greatest changes were seen in vagotomized rats at 3 and 24 h. The physiological mechanisms of these pathological states are discussed.