OBJECTIVE The primary efficacy and safety of Mircette (brand of desogestrel/ethinyl estradiol and ethinyl estradiol), an oral contraceptive containing 150 microg desogestrel and 20 microg ethinyl estradiol given for 21 days, followed by 2 days of placebo and then 5 days 10 microg ethinyl estradiol, was evaluated. METHODS In a large, open-label, 18-month, multicenter trial, a total of 1143 of 1250 healthy female subjects contributed to the determination of extent of exposure, for an equivalent of 1080.8 woman-years of use. RESULTS Absence of withdrawal bleeding occurred in 5.5% of total cycles and intermenstrual bleeding occurred in 12.0% of total cycles. Breakthrough spotting was more common than breakthrough bleeding. The Pearl Index for total pregnancies during treatment was 1.02/100 woman-years. Fewer than 3% of subjects discontinued study participation, primarily because of menstrual problems, indicating that Mircette was an oral contraceptive acceptable to the women studied. Overall 73.6% of all subjects reported one or more adverse events, and a total of 43.9% of subjects reported drug-related adverse events. The most common drug-related adverse events reported included headache (8.5%), breast pain (7.3%), dysmenorrhea (4.2%), and menstrual disorder (4.2%). There were no reports of venous thromboembolic events or of significant changes in blood pressure, lipid metabolism, or serum glucose level. CONCLUSIONS The study confirmed that Mircette is a safe and efficacious oral contraceptive that is well tolerated and acceptable to women who have previously used oral contraceptives, as well as first-time users.