Rubber materials are used normally in large deformations, that is, in nonlinear conditions. So, nonlinear viscoelasticity is important for the characterization of rubber materials. So-called Payne effect, strain amplitude dependence of dynamic modulus, is one of the examples for nonlinear behaviors in rubber materials.In linear viscoelasticity, we can determine experimentally peak stress, peak strain, and phase angle difference in stress and strain waves. Hence we can define storage and loss modulus, GЈ and GЉ, respectively. In nonlinear viscoelasticity, however, stress wave deviates from a simple sinusoidal wave. Therefore, we may discuss Payne effect on rubber materials by absolute values of dynamic modulus, |G*|. We need additional information on viscoelasticity to discuss Payne effect.In this work, strain amplitude, g L, and phase angle, wt, dependence of differential dynamic modulus, G*(w, g L ; t) for carbon black filled, cured and unfilled, cured SBRs were tested in large amplitude oscillatory shear (LAOS) at g L ϭ0.005 Ϫ2.0 and n L ϭ0.001 Hz (period Tϭ1000 s) using self-made biaxial rheometer. Small oscillations (g S ϭ0.005, n S ϭ0.2 Hz) were superposed orthogonally on LAOS. Strain softening in G* was found depending on both g L and wt. Unfilled, cured rubber showed affine-like change with LAOS in both GЈ and GЉ, while filled, cured rubber did partial recovery in GЈ at peak position of LAOS and additional enhancement in GЉ. As a result, filled, cured rubber showed much higher values of differential loss tangent (DLT) in LAOS than unfilled, cured one, indicating that DLT may be useful for novel index of heat generation in periodical deformations of rubber materials.