In 7 adult dogs (2 [female], 5 [male]), rendered anemic by removal of 1/2 the determined blood volume, and observed for 12 wks., % total blood volume was unaltered throughout; erythrocyte count was normal by the 8th wk., and thereafter rose above normal (prehemorrhage) level; the. diameter of the erythrocytes decreased from an average of 6.9 [mu] before, to an average of 6.1 [mu] at end of post-hemorrhagic period. Throughout the post-bleeding period there was a steady decrease in the proportion of normal size cells and an increase in the proportion of cells of much smaller size. Curves illustrating the scatter in cell diameter show that the normal curve is fairly symmetrical and has a narrow spread. The curve for hemorrhagic anemia lies to the left of the normal, has a wider spread, and is asymmetrical in type. Calculation of the individual red cell volume showed a steady diminution in cell volume which was synchronous with the decrease in cell diameter. The coefficient of correlation between the cell diameter and cell volume was + 0.8230 [plus or minus] 0.0220. A rapid increase in the number of red cells was associated with a marked decrease in cell diameter and individual cell volume. The coefficient of correlation for cell count and cell diameter was [long dash]0.4666 [plus or minus] 0.0533 and for cell and cell volume, [long dash]0.5856 [plus or minus] 0.0448.