The activation energy for a heterogeneous reaction involving a solid may be obtained from a plot of integral(0)(alpha) In(d alpha/dt) d alpha against integral(0)(alpha) (1/T) d alpha, where alpha represents the fractional conversion of the solid reactant, and T(t) is the (time-dependent) reactant temperature. This new approach to the analysis of dynamic thermoanalytical kinetic data has distinct advantages over existing methods, as it needs to make no assumption about the kinetic model, involves no approximation to the temperature integral, and is easy to implement on the computer.