In a randomized, single-blind study, of a pilot nature, the administration of terbutaline sulphate was found to cause significant inhibition of contractions in premature labor. This effect became evident within 30 min when the dosage was 0.1 mg in 1 ml cellulose gel, applied vaginally, and within 2 h when released from a 5-g medicated vaginal polymer ring containing 10% terbutaline sulphate. No generalized effects of the terbutaline were noted (such as increased blood pressure or tachycardia) and the level of terbutaline in peripheral venous blood remained low. Vaginally administered terbutaline can obviously be quickly resorbed, giving a localized effect. Thus applied, terbutaline would appear to offer a number of advantages as regards treatment procedure.