The unique, quasi-one-dimensional feature of TlxV6S8 caused by a rigid V/S framework with parallel channels occupied by Tl atoms has been studied by voltammetric methods. Single-crystal electrodes exhibit two redox reactions at ca. 0.2 V vs. Ag/AgCl and ca. -0.4 V vs. Ag/AgCl which are nearly independent of each other. The peak at 0.2 V is due to the de-intercalation of Tl from the host lattice, whereas the wave at -0.4 V is attributed to the injection of electrons into the conduction band of the V/S framework with concomitant intercalation of cations from the electrolyte. Both redox processes are shown to exhibit Nernstian behaviour, i.e. the heterogeneous charge transfer across the electrode/electrolyte interface is relatively fast. The current is controlled predominantly by linear semi-infinite diffusion of the respective species within the channels of the electrode : Tl atoms for the redox process at 0.2 V and K+ ions for the redox process at -0.4 V in the presence of K+ in the electrolyte. From voltammetric and potential step measurements the apparent diffusion coefficient of Tl in Tl0.8V6S8 was determined to be about 10(-7) cm(2) s(-1).