Thirty-five pre-menopausal women were treated for 3 mth with sequential combinations containing oestradiol valerate and levonorgestrel in two different doses. Three treatment cycles, and 2 cycles before and 2 after treatment were studied. Subjective symptoms were relieved in 62% of women during treatment. Normal secretory phase was observed in 25–53% before and 33–35% at the end of treatment. Serum FSH and the frequency of serum progesterone increase > 5 nmol/1 decreased, particularly during treatment with the higher dosage. Ovulations occurred during both treatments; these combinations cannot therefore be used for contraceptive purposes. In ultrasonic studies, the average volume of ovaries in which no follicles were found, was 7.6 cm 3. The volume of ovaries with follicles was 10.5 cm 3. The follicular growth was often defective, also in ovulatory cycles, in both treatment and control cycles. In ovulatory cycles, luteinized unruptured follicles occurred in 2% before treatment and in 5% during treatment. In anovulatory cycles, persistent follicles were observed in 13% before treatment and in 19% during treatment. The frequency of luteinized unruptured follicle (LUF) syndrome did not increase significantly in pre-menopausal women during oestrogen-progestin treatment. However, persistent follicles were frequent during anovulatory cycles. Serum oestradiol concentrations correlated significantly with the diameter of the dominant follicle. No significant changes were found in uterine volume. Both of the tested regimens are useful for treatment of pre-menopausal symptoms.