Elasticity and viscosity, of fully relaxed and gradedly contracted arterial wall, were measured on spirally cut rabbit aortic strips suspended in Ringer's solution. Pre-extended contracted tissue submitted to additional stretch shows an instantaneous and a slow elongation. Only instantaneous elongation was observed on fully relaxed tissue. This behavior can be simulated by a mechanical model consisting of a spring in series with a dashpot, and a second spring in parallel with the first spring–dashpot component. The modulus of the first spring and the coefficient of viscosity both increase steadily with increasing contraction, while the modulus of the second spring decreases. The first spring–dashpot component is believed to represent the viscoelastic behavior of smooth muscle on its non-contractile network. The second spring probably represents the combined elastic properties of arterial elastin and collagen.