Abstract This study presents the advantages of chloride media as a leaching media for sulfide minerals. The advantage in using cupric chloride solution as a leaching media is its ability to form complexes, which increases the redox potential and thus the oxidative power of the solution remarkably. The thermodynamics of the solution are discussed and the prevailing species suggested. Cuprous ion can be suggested to be present mostly as [CuCl3]2- but also partly as [CuCl2]-. The complexation of cupric ion is more inconsistent, but it can be suggested that cupric ion is not totally in a complex form. With lower chloride concentrations Cu2+ may not form complexes. At high Cl concentrations [CuCl]+ or [CuCl3]- and [CuCl4]2- may be present. Some chloride based processes are presented and the advantages of them are compared. The most important processes are CLEAR, CYMET and HydroCopper®, of which the latter has recently reached the commercial scale. One of the advantages in HydroCopper® is that 95 % of the sulfur can be turned into the elemental form. Also the five step solution purification starting from Cu2+ and sulfate removal, silver removal, neutralization, ion exhange and ending in Cu2O precipitation is a good base for high quality copper production. The unit processes used in HydroCopper® are not new, but the innovative combination of known unit processes makes HydroCopper® unique.