Geometry, electronic structure, and electron affinity of d(1) transition metal chloride clusters (MCln, M = Sc, Y, La; n = 1-5) have been calculated using density functional theory. Chlorine atoms are chemically bound in all cases except for MCl5. The electron affinities of MCln (n = 1-3) are small and increase only marginally as a function of n until the valence of the metal atom is consumed. Beyond this, they rise sharply and reach a value of 5.96, 6.03 and 5.90 eV for ScCl4, YCl4 and LaCl4, respectively and remain high for n = 5. MCln, (n = 4,5) clusters, therefore, behave as superhalogens. Results are compared with available experimental data. (C) 2010 Published by Elsevier B.V.