A combined electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) instrument was used to monitor the mobile species transfers associated with the redox processes of thin (Gamma congruent to 100-150 nmol cm(-2)) alpha- and beta -nickel hydroxide films exposed to aqueous LiOH solution. A comparison of the measured PBD signal with the predicted PBD profiles, calculated by temporal convolution analysis of the current and mass responses, enabled the contributions to redox switching of anion (OH-) and solvent (H2O) transfers to be discriminated quantitatively. The responses from the combined instrument are reconciled in terms of H+ deintercalation/intercalation within the nickel hydroxide structure as OH- ions enter/exit the film. Hydroxide ion movement is associated with a counterflux of water. Thin nickel hydroxide films show a gradual alpha-->beta phase transformation with continuous voltammetric cycling, especially when the films are exposed to high concentrations of electrolyte. alpha -Films are characterised by OH- transfers that dominate the H+ and H2O movements; beta -films are characterised by an increased participation of water and protons to the exchange dynamics.