Wyeth Laboratories is seeking US Food and Drug Administration approval to market an oral contraceptive (OC), Triphasil, that delivers varying doses of estrogen and progesterone during each part of the menstrual cycle. The pill is already being marketed in Germany and the United Kingdom under the name Trinordiol. Triphasil provides an increased estrogen dosage at midcycle (30 mcg at days 1-6, 40 mcg at days 7-11, and 30 mcg at days 12-21) and an increased progesterone dose as the cycle progresses (50 mcg at days 1-6, 75 mcg at days 7-11, and 125 mcg at days 12-21). The low progesterone dose during the early part of the cycle is thought to be beneficial because the progesterone component of OCs has been linked to increased cholesterol levels. Wyeth's studies of more than 3546 women demonstrated high acceptability and an unplanned pregnancy rate of 0.33 pregnancies/100 women years. No cases of thromboembolism or other serious complications were noted in more than 35,000 cycles. Change in vaginal bleeding, which occurred in 2.9% of the women, was the most common medical reason for discontinuation. 78% of 109 women who conceived after discontinuing Triphasil became pregnant within 6 months. Triphasil is considered to be a suitable contraceptive for any woman in whom OCs are not contraindicated. However, its low steroid dose may not be sufficient to control conditions such as irregular bleeding, excessive bleeding, or dysfunctional bleeding.