We have investigated the scaling relationship between rheological behavior and concentration for both salt-free and saline solutions of hyaluronan (HA), and adopted three viscoelastic constitutive models to predict the linear/non-linear viscoelastic behavior of these aqueous solutions of HA with different molecular weights at different concentrations up to 20 mg/ml. A series of concentration equations are obtained to describe the influence of HA concentration on solution viscosity. Corresponding to dilute and semi-dilute concentration region, salt-free HA solutions have scaling relationship between specific viscosity and HA concentration as eta(sp) similar to c(1.0) and eta(sp) similar to c(3.5), respectively, while for 0.15 M NaCl HA solutions, the scaling exponents are 1.5 and 4.2, respectively. Simulation results indicate that these constitutive models have good applicability to describe quantitatively the rheological properties of HA entangled solutions under either dynamic or steady shear flow. In addition, the plateau modulus scaling of HA solutions can be well described by the concentration-dependent length scale. (C) 2013 Elsevier Ltd. All rights reserved.