Determination of density distribution of erythrocytes in preeclampsia in late pregnancy was performed using a method in which blood cells are separated according to their density by differential flotation. The cumulative density distribution curve of the erythrocytes of preeclamptic patients was evidently shifted to the left, representing a denser cell population as compared with healthy women prior to delivery. The density distribution curve of preeclamptic women resembled the curve of nonpregnant young women. The largest differences were observed in separating fluids No. 9 of specific gravity 1.106 (p = 0.0351), No. 11 of specific gravity 1.098 (p = 0.0018) and No. 13 of specific gravity 1.090 (p = 0.0026). The resemblance of the density distribution curve of erythrocytes of preeclamptic patients with that of nonpregnant women may indicate a similar age distribution of erythrocytes or may reflect cellular dehydration resulting in higher density of erythrocytes in preeclampsia.