In a group of patients receiving intraamniotic injection of prostaglandin F2alpha or intramuscular injection of a methyl analogue of prostaglandin E2 for the termination of pregnancy, significant ariway constriction was demonstrated. The greatest responses were seen in 2 patients who had personal or family histories of asthma. If such patients receive prostaglandins, they should be carefully monitored to detect clinically important airway obstruction.