The preparation of pure alkaline metal hydroxides (NaOH, KOH, RbOH, CsOH), their proton diffusion coefficients (D-H) obtained from PFG-NMR measurements and proton conductivities (sigma) measured by complex impedance spectroscopy are reported for the cubic high temperature phases and melts. For nominally pure material, the measured conductivities are very low, but still due to impurities in terms of water content, whereas proton diffusion is found to be very high (approximate to 10(-7) cm(2) s(-1)) and well reproducible. The unusually high Haven ratios (D-H/D-sigma) of greater than 10-1000 are suggested to be the result of a proton transport mechanism involving correlated proton transfer events, which are discussed in detail.