The behaviour of arsenic, antimony, and bismuth during electrolytic re. ning of copper has been investigated using cyclic voltammetry, scanning electron microscopy, X-ray diffraction analysis and Auger electron spectroscopy. Electrodeposition was conducted using Group 15 element additions to two different cupric sulfate electrolytes: commercial tank house electrolytes containing 45 g l(-1) Cu2+ and 200 g l(-1) H2SO4 and liberator cell conditions containing 10 g l(-1) Cu2+ and 400 g l(-1) H2SO4. Analysis of electrochemical kinetic parameters indicates that the copper cathodes were more active at the higher sulfuric acid concentrations. SEM analysis revealed that Sb and Bi additions promoted truncated copper crystals while As-containing electrolytes produced random crystals. XRD patterns indicated Group 15 elements favour the production of (2 2 0) crystallographic orientation. Surface analyses of the copper deposits using AES techniques show that arsenic and antimony are deposited electrochemically forming primarily solid solution phases with copper in commercial tank house electrolytes. Under liberator cell conditions, a Cu3As intermetallic phase forms when arsenic is present in the electrolyte. Antimony is present in solid solution under these conditions. Reduction of bismuth was not detected during these experiments.