Objective The safety and contraceptive efficacy of a new 24-day regimen of an oral contraceptive combination containing gestodene (GTD) 60 mu g and ethinylestradiol (EE) 15 mu g was evaluated in an open-label, multicenter study. Methods Adult women received GTD 60 mu g/EE 15 mu g from day 1 to 24 and 4 days of placebo during a 28-day cycle for either 13 or 19 cycles. Results Of the 1515 subjects enrolled, 1496 were included in the intent-to-treat analysis. A total of three pregnancies were reported during the 18 194 treatment cycles of the study, yielding a Pearl index of 0.21. Life-table analysis, based on 16 954 cycles, gave an accidental pregnancy rate of 0.0033. The most frequent adverse events were headache (reported in 35% of subjects), absence of bleeding (16%), flu-like syndrome (15%), pharyngitis (15%) and abdominal pain (15%). The most frequent reasons for withdrawal from the study were metrorrhagia, flu syndrome and absence of bleeding. Analyses of withdrawal and intermenstrual bleeding and spotting indicated acceptable cycle control. Conclusions The 24-day GTD 60 mu g/EE 15 mu g, regimen appears to be a well-tolerated and effective method for low-dose oral contraception. The current formulation offers an ultra-low steroidal dosage combined with a reduced pill-free interval to improve contraceptive efficacy.