sampling was performed twice before application and then after 1/4, 1/2, 1, 2, 4, 6, 8, 24 and 48 hours. Serum was analysed for unconjugated and conjugatedestriol (E3), FSH and LH by radio-immunoassay. Considerable interindividual variations in serum levels of unconjugated E3 were found but mean values were about equal throughout the study for the two preparations. Peak levels of 0.5-0.6 nmol/l were