A slowly-absorbed aqueous suspension of betamethasone, intended for use in the induction of parturition, was administered to 10 cows. Each cow received 2ml (mean individual dose, 44.4 ± 0.5𝛍g/kg) by subcutaneous injection. Plasma samples were collected on six occasions over a seven-day period before treatment and on 21 occasions over a 29-day period after treatment. The mean concentration of betamethasone in plasma, as measured by radioimmunoassay, peaked at 0.6ng/ml 24 hours after injection and was detectable for four days. Depression of the endogenous Cortisol levels, as recorded with other long-acting synthetic glucocorticoids, was observed with this preparation of betamethasone. Plasma glucose was significantly elevated for eight days after betamethasone administration.