The concentrations of plasma LH, FSH, estradiol, and progesterone, as well as urinary LH, were measured during the last treatment cycle and during the recovery cycle in women who, immediately after abortion, had started microdose combined oral contraceptives containing 30 μg of ethinylestradiol and 150 μg of d-norgestrel. During the treatment, cyclic variations were found in LH, FSH, and estradiol concentrations. FSH levels were highest during the first treatment week as well as the treatment-free week. LH concentrations were highest during the first treatment week. Estradiol concentrations showed a significant increase during the treatment-free week and during the first treatment week suggesting a follicle stimulation. The recovery of ovulation occurred rapidly, in a great majority of the subjects, after discontinuation of the treatment. The first midcycle LH peak was observed thirteen days after the intake of the last pill, and 50% of the subjects had ovulated within 22 days. In 91% of the subjects, plasma progesterone concentration during the luteal phase was higher than 5 ng/ml.