To study the RHEOLOGICAL behaviour of Caspian pony blood which is a suspension of macromolecules in an aqueous medium, steady shear and small amplitude oscillatory shear experiments were conducted on thirty Caspian pony blood samples. The seven different viscoelastic constitutive equations viz., Giesekus, Thurston, four-constant Oldroyd, Williams-Bird, Spriggs, modified Spriggs and Bogue-White were examined. The viscosity data obtained from steady shear experiments and the dynamic viscosity and imaginary part of complex viscosity data obtained from oscillatory shear experiments were used to determine the model parameters. The performance of the models was studied by comparing their prediction for viscosity, dynamic viscosity and imaginary part of complex viscosity with those measured experimentally. As a result, Giesekus and Thurston models were found to be the best models and the Caspian pony blood was characterized by these models. The same experiments mentioned above were carried out on four blood samples of one Caspian pony, different only in hematocrit, in order to find its effect on RHEOLOGICAL properties of Caspian pony blood. It was concluded that as the hematocrit of Caspian pony blood increased, the zero shear rate viscosity, the relaxation time, the retardation time and the very high shear rate viscosity increased and the mobility factor decreased.