The conductivity of three thulium (Tm) salts has been studied in dimethylsulfoxide (DMSO) at 298 K. Tm(NO3)(3) has strong electrolyte properties in DMSO. Cyclic voltammetry has been used to investigate the electrochemical behavior of the Tm3+ ion in 0.01 mol L-1 Tm(NO3)(3)-0.1 mol L-1 LiClO4-DMSO system on the Pt electrode at 299 K. The experimental results of cyclic voltammetry indicate that the reduction of the Tm3+ ion is an irreversible process. The transfer coefficient and the diffusion coefficient of Tm3+ ion have been measured. In a nonaqueous system, the surface of Tm-Co alloy films prepared by the potentiostatic deposition technique is uniform, adhesive, compact, and showed a metallic luster. Tm-Co alloy films are amorphous, as proven by X-ray diffraction spectrometry. Tm-Co alloy films have soft magnetic property at 293 K. This kind of rare earth film prepared from organic solvent could have the potential application as a magnetic material. (C) 2004 The Electrochemical Society.