A new set of expressions has been derived for the determination of the activation energy E of a thermoluminescence (TL) peak. Unlike those previously existing in the literature, the present expressions take into account the variation of the symmetry factor mu _g(x) with U_m(=E/kT_m) where x is the fractional intensity, k the Boltzmann constant and T_m the peak temperature and prior knowledge of the order of kinetics b is not required. The applicability of the present expressions have been tested using both numerically generated and experimental thermoluminescence peaks.