AIM: To determine the viscoelastic properties of the porcine lens METHODS: Linear viscoelastic shear properties of the stroma of four porcine lenses were measured within 5 hours post-mortem, using sinusoidal oscillatory shear deformation. The elastic shear modulus, viscous shear modulus, dynamic viscosity, damping ratio, and phase shift of the lenses were quantified by a controlled-strain, linear simple-shear rheometer at frequencies of 10-50 Hz. RESULTS: The mean viscoelastic properties and their standard deviations across the frequencies examined were: the elastic shear modulus, G' = 6.2+/-4.0 Pa, the viscous shear modulus, G'' = 19.2+/-2.5 Pa, the dynamic viscosity, eta' = 0.16+/-0.1 Pa x sec, the damping ratio zeta = 4.06+/-1.25, and the phase shift, delta = 76 degrees +/- 5.6 degrees. CONCLUSIONS: The measured viscoelastic shear properties of the porcine lens reflect a low dynamic viscosity with a high damping ratio. The porcine lens is viscoelastic and is more viscous than elastic. The magnitude of the complex shear modulus of the porcine lens, |G*|, is similar to the shear modulus of the young human lens. Understanding these viscoelastic properties of the natural lens may provide guidance in developing a lens substitute capable of accommodation in the post cataract patient.