A dose-response study using PGE2 in a viscous gel has been undertaken for induction of midtrimester abortion. A direct relationship was found between the time to abortion and the dose administered. However, even using PGE2 3.5 mg induced uterine activity was noticed to subside in a significant number of women after approximately 6 h. For routine management it is suggested that PGE2 3.5 mg be injected and followed by repeat doses 6 h later with removal of the injecting catheter on each occasion.