The proposed treatment of willemite ore at Port Pirie by E-Z would entail a slag fuming type operation to produce raw zinc oxide fume containing an appreciable percentage of lead. This lead rich fume would be deleaded in a rotary kiln and the densified zinc oxide product shipped to Risdon, Tasmania. This report describes a series of tests carried out for E-Z in the BHAS Research Pilot Rotary Kiln, that attempted to reproduce overseas deleading practice. The preliminary investigations described in the report appendix were designed to determine the preferred form of carbon required for the elimination of lead from the fume, and to establish optimum operating conditions. In the later stages of this work, the significance of the distribution of arsenic between the products of a deleading roast became apparent, so close attention was paid to establishing mass balances for zinc, lead, arsenic and the halogens, fluorine and chlorine, over the kiln in each test. If arsenic reported in the baghouse fume, the treatment costs for this material at Port Pirie would be greatly increased. A series of dehalogenating roasts were performed to determine the behaviour of arsenic at lower temperatures (830-1130 degrees Centigrade).