The “Thermal Activation Compensation Effect”, reported in many temperature activated experiments, is reviewed. The effect describes the observation that in some cases, families of Arrhenius curves plotted vs. a compensation variable, intercept at a finite temperature called the compensation or isokinetic temperature T0. It is shown in this work that the effect is real, in the sense that T0 was obtained within the experimental range and not by graphical extrapolation. The case of intrinsic charge carrier concentration in semiconductors vs. temperature, with bandgap as a compensation variable allows one to probe into the origin of T0 by reference to an available detailed theory. The conclusion drawn is that the compensation temperature is mathematically a reflection of the dependence of activation energy on the temperature and compensation variable in the cases discussed. Hot carrier effects are suggested to account for this phenomenon. © 1991 IOP Publishing Ltd.