This paper reports that the crossing-point temperature (CPT), where the heat conduction diminishes at the centre of a symmetrical exothermically reactive solid (or an assembly of packed solid particles), can be considerably different from the set oven temperature during a transient bask:et heating procedure for measuring exothermic reactivity. The CPT differs from the oven temperature by a larger amount for a greater oven temperature and is also dependent upon sample size and the nature of the materials concerned. The experimental evidence of such differences, derived from various previous studies, is illustrated here. Such differences can, under certain circumstances, lead to considerable variations in the estimation of the kinetic parameters for the two existing transient testing procedures. This is an important point of consideration for future work in the area of thermal ignition of particulate materials.