The effect of a newly developed tocolytic oxytocin analogue, 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-oxytocin on lipid and carbohydrate metabolism was investigated. Oxytocin and vasopressin both stimulated lipogenesis in isolated rat adipocytes, an effect which was dose-dependently inhibited by the oxytocin analogue. In vivo, intravenous injection of 10 nmol/kg body weight of the analogue to 11 healthy subjects caused an initial, but insignificant peak after 4 min in both plasma glucose and glycerol, which thereafter remained at basal level. It is concluded that although an antagonistic effect of the analogue on vasopressin- and oxytocin-stimulated lipogenesis could be demonstrated in vitro, the effect on lipid and carbohydrate metabolism in vivo in humans is insignificant.