The effect on the log plot, used to determine the activation energy (E) and the frequency factor (A), when using data derived from DTG peaks from two independent reactions, but which are in close temperature proximity, is discussed. It is shown that, while it is possible to derive activation energy information from such data when the peaks are of nearly equal size, the log plot produced from similar peaks having widely differing peak areas (i.e. widely differing E and A values) is non-linear. In this situation, it is impossible to derive either of the E values. The practice of drawing the statistically best straight line on such log plots has no meaning, and is not to be recommended, because it gives misleading results. Preliminary results from data derived from interacting reactions are also discussed.