A trial was conducted to determine the efficacy of dietary molybdenum (Mo) and sulphur (S) in reducing liver copper (Cu) levels in sheep at risk of Cu toxicity. Sheep were fed 75 mg Cu/day during a preliminary period to establish high Cu levels in their liver. For a period of 47 days the sheep were fed varying levels of Mo (0 – 140 mg/day) and S (0 – 4 g/day) with no added dietary Cu. Within 8 days of the commencement of Mo feeding, sheep in the highest Mo groups (140 mg/day) developed Mo toxicity. Six sheep in these groups were slaughtered on day 13, the remainder were fed 70 mg Mo and 50 mg Cu per day. Sheep fed 70 mg Mo/day (without Cu) showed a 40% reduction in liver Cu compared with groups receiving no Mo supplement. When extra Cu was fed with 70 mg Mo, no reduction in liver Cu was observed. Elevated kidney and plasma Cu levels were found in all groups receiving supplementary molybdenum. A dietary supplement of 70 mg Mo for a restricted period is recommended to reduce liver Cu in sheep (SA Mutton Merinos) provided dietary Cu levels are simultaneously reduced.