The possibility of altering bone collagen turnover rates by injecting large doses of dexamethasone or by administering large doses of cyclophosphamide orally was investigated in sheep on low and high dietary intakes by measuring changes in the ratios of free and total hydroxyproline to creatinine and of calcium to creatinine in the urine. Dexamethasone at the rate of 1·15 mg/kg live weight caused an increase in free hydroxyproline excretion of 111 and 26 % and in calcium excretion of 402 and 243 % in the low and high intake sheep respectively. Cyclophosphamide (10 mg/kg) had little effect except for causing a slight decrease in total hydroxyproline excretion in the sheep on the high dietary intake. Heavier sheep on high dietary intakes excreted more free hydroxyproline than lighter sheep on low intakes.It was concluded that dosing sheep with corticosteroids for the purpose of defleecing could cause abnormal collagen metabolism. Skeletal disorders are a likely result but further long-term field work would be necessary to determine the practical significance of these findings.