The extraction of Au(III) by tri-n-dodecylammonium chloride (TLAHCl) has been studied by measuring the distribution coefficient of the metal as a function of the TLAHCl concentration at 0·5, 1 and 2 ionic strength. Results indicate the formation of the species AuCl3(TLAHCl) and AuCl3(TLAHCl)2in the organic phase. The formation constants vary linearly with the ionic strength. By using the Specific Interaction Theory the interaction coefficient between AuCl4and H+has been estimated.