The kinetics of the transition γ→β Li₂ZnSiO₄ have been studied in the range 480–855 °C and in the reverse direction over the range 906–940 °C. X-ray powder diffraction was used to determine the degree of transformation in powdered samples annealed isothermally for various times. At most temperatures, the data could be analysed using the Johnson–Mehl–Avrami equation and a rate constant value extracted. At two temperatures, 480 and 855 °C, the data appear to fit an autocatalytic rate law. The effect of particle size on transformation rate was studied at one temperature, 572 °C; the rate increased with decreasing particle size. An Arrhenius plot of rate constant data was constructed; below ca. 780 °C, a straight line was obtained for the γ→β transformation with an activation energy of 147 ± 20 kJ mol^–1. As the equilibrium transition temperature, 880 ± 20 °C, was approached the transition rates in both directions decreased increasingly rapidly. In the range ca. 860–900 °C no detectable transformation in either direction occurred for heating times of up to two weeks. The temperature dependence of the γ→β transition rate has been modelled satisfactorily by regarding the transformation as a modified, microscopically reversible transformation at all temperatures, subject to the constraint that macroscopically the phase rule must be obeyed. The rate data have also been presented on a time–temperature–transformation diagram. The enthalpy of the β⇌γ transition was determined by d.t.a. as 3.8 ± 1.0 kJ mol^–1.