In order to study the marked variation of red blood cell sedimentation rate in some species of animals, the packed cell volume, volume percentage of erythrocytes in whole blood, was reshuffled of 20%, 40% and 60% using heteroplasma of chicken and goat, and the red blood cell sedimentation rate was measured in Westergren tubes at 27+-1 deg C and 8+-1 deg C. The values of packed cell volume (PCV) of goat and chicken were 40.7+-4.1% and 30.2+-2.2% respectively. The sedimentation rates of reshuffled red blood cell were settled faster at lower PCV than higher PCV, i.e. there was a reverse relationship between the sedimention rate and PCV. Red blood cells of chicken settled quickly, where as those of goat settled very slowly. Chicken red blood cell sedimented rapidly even in goat plasma, and goat red blood cell sedimented slowly in chicken plasma. These findings indicate that the plasma is not the only factor determining the rapid red blood cell sedimentation rate of chicken. The sedimentation rate of reshuffled red blood cell of chicken and goat were accelerated at higher temperature than lower temperature.