The extraction of Cu(II) from 5.0 M lithium chloride solutions using tri-n-dodecylammonium chloride (TLAHCl) dissolved in toluene was studied at 25°C. The data were treated both graphically, by the normalized-curves methods, and numerically using the LETAGROP-DISTR program. In both cases, the extraction of copper was best explained by the formation of the species (TLAHCl2)CuCl2 and (TLAHCl)5CuCl2 in the organic phase. The formation constants for the different species were obtained at different ionic strengths (1.0-5.0 mol dm-3) and correlated using the specific-interaction theory. © 1986.