Anisotropic melt polyester, based on chlorohydroquinone and terephthalic acid modified with 4,4''-biphenol and isophthalic acid, was prepared by esterification reaction of corresponding diols and diacids. This polymer showed thermotropic liquid crystal behavior, which was evidenced by DSC and DTA methods. Rheological properties of this polymer were determined using an Instron capillary rheometer. The melt viscosity first decreased with increasing temperature but then passed through a minimum and increased with further increases of temperature at all shear rates considered. The flow index tended to increase and the yield stress was observed at low shear stress with the onset of liquid crystalline order. These results were qualitatively interpretated with a rigid flow unit, which was assumed to be a nearly parallel aggregate of rigid chains.