Tests of the strain sweep, frequency sweep, and stress relaxation for raw epoxidized natural rubber were carried out with a rubber processing analyzer. The results showed that the complex viscosity, eta*, decreased with the prolongation of the aging time in the region of Newtonian flow, but in the region of non-Newtonian flow, the decrement of -o* with a rising shear rate decreased with the prolongation of the aging time. The torque (S') response from the strain sweep indicated that aging brought about an obvious decrease in the increment of S' with rising strain in the linear viscoelastic region and a small increase in the slope of the plateau on the curve of the S' response in the nonlinear viscoelastic region. The stress relaxation rate constants k and b, calculated according to the equations S-t = S(0)e(-kt) and S-t = S1t(-b) (where S-t, S-0, and S-1 are the stresses at relaxation time t, t = 0, and t = 1, respectively), increased, and the stress relaxation time obtained directly from the rubber processing analyzer shortened with the prolongation of the aging time. (c) 2006 Wiley Periodicals, Inc.