Linear viscoelastic equations have been presented for the creepT-jump experiment, a technique which has been used to determine apparent activation energies for viscoelastic deformation processes. The equations describe the creep rate at any time,t, before and after a rapid change in temperature. These equations were solved for various cases using realistic forms for the retardation spectrum, a box and a wedge distribution. A straight line was predicted for creep rate data plotted against time on log-log coordinates for times before the imposed temperature change att′. In general, a curve will be seen on the same plot for data obtained aftert′; the exact form of this curve depends upon the value ofΔHa and the shape of the retardation time distribution. The box distribution was used to find the effect ofbT on the creep rate at times after theT-jump and on the determination ofΔHa in experimental circumstances. The magnitude of the effect was not as great as had been previously thought, and a method by which the problem could be overcome was suggested.