Cyclic voltammetry and chronopotentiometric and chronoamperometric curves were used to study the electroreduction of Lu3+ in a LiCl + DMSO system. The electrode process of Lu3+ reduced on a Pt electrode occurs in one step: Lu3+ + 3e(-) --> Lu. The transfer coefficient and diffusion coefficient of Lu3+ in the 0.1 mol dm(-1) LuCl3 + 0.1 mol dm(-3) LiCl + DMSO system were calculated as 0.141 and 2.86 x 10(-10) m(2) s(-1) at 305 K, respectively. The experimental results indicate that a Lu-Co thin film containing 5.65-56.30 wt% Lu was obtained by potentiostatic electrolysis in 0.1 mol dm(-1) LuCl3 + 0.1 mol dm(-3) CoCl3 + 0.1 mol dm(-3) LiCl + DMSO. The surface of the Lu-Co thin film observed by scanning electron microscopy (SEM) was uniform, adhesive and had a metallic luster. The Lu-Co thin films obtained were amorphous as proven by X-ray diffraction analysis (XRD). (C) 2003 Elsevier B.V. All rights reserved.