The clinical signs of camel sway disease in the Hexi Corridor of Gansu province were defined. The contents of eight minerals in soils, in forage and in the blood and hair of bactrian camels from this region were determined. The related blood indices were also measured. The concentration of molybdenum in soils and forage was 4.8 +/- 0.02 and 4.8 +/- 0.25 micrograms/g (dry matter), respectively, the copper to molybdenum ratio in the forage being only 1.3. The concentration of copper in blood and hair from the camels was 0.28 +/- 0.17 micrograms/ml and 3.50 +/- 1.00 micrograms/g, respectively. There was a hypochromic microcytic anaemia and a low level of ceruloplasmin in the blood. It is therefore suggested that sway disease of bactrian camels in this region is caused by secondary copper deficiency, mainly due to the high molybdenum content in soils and forage. The copper deficiency in the camels was aggravated during reproduction. Oral administration of copper sulphate can prevent and cure the disease.