The rate of the bromine-exchange reaction between gallium bromide and i-butyl bromide in 1,2,4-trichlorobenzene or nitrobenzene was measured at 19, 25 and $40^{circ}C$, using i-butyl bromide labelled with Br-82. The results indicated that the exchange reaction was second order with respect to gallium bromide and first order with respect to i-butyl bromide. The third-order rate constant determined at $19{circ}C$ was $3.28{ imes}10^{-2}l^2{cdot}mole^{-2}{cdot}sec^{-1}$ in 1,2,4-trichlorobenzene and $9.25{ imes}10^{-3}l^2{cdot}mole^{-2}{cdot}sec^{-1}$ in nitrobenzene. The activation energy, the enthalpy of activation and the entropy of activation for the exchange reaction were also determined.