Both theoretical and experimental investigations on proton conduction and diffusion in Li2SO4 have been carried out in this work. A theoretical method has been developed based on Fick’s diffusion theory to calculate the proton diffusivity under an external electric field. Using the results obtained from de polarisation measurements the proton diffusivity has been calculated to be of the order of 10(-5) cm(2) s(-1) for alpha-Li2SO4. Using de conductivity values, a calculation has been made to determine the proton concentration in the sample. The concentration obtained is of the order of 10(19) to 10(20) cm(-3) with small structure dependence. The proton concentration is only about one percent of the Li+ ions, so the protons exist as an impurity in the sample. Nevertheless, these protons are very mobile, resulting in high conductivities and diffusivities.