The equilibrium constants of copper and iron were determined for the copper (II)-iron (III)-LIX984-Orfom SX-1 system. The average equilibrium constants of copper (II) and iron (III) were estimated to be 15.0+/-4.2 and 0.00030+/-0.00013 respectively. The results of extraction experiments show that LIX984 is a very selective copper (II) extractant. On the other hand the extraction of iron (III) by LIX984 is very low. Results also show that higher extraction temperatures leads to higher rate of copper extraction. (C) 2000 Elsevier Science Ltd. All rights reserved.