Following a brief review of the progressive improvements in oral contraceptive (OC) formulations and a description of the multicenter international study of Triella, this article describes a French multicenter double-blind study which compared the triphasic OC Triella with the widely used biphasic pill Adepal. Triella combines a constant dose of 35 mcg ethinyl estradiol (EE) with norethisterone doses of .5 mg for 7 days, .75 mg for 7 days, and 1 mg for 7 days. 91 women used Triella for a total of 463 cycles and 87 used Adepal for 412 cycles. There were no statistically significant differences in the age, height, weight, blood pressure or previous OC usage of the 2 groups. Average menstrual cycle length and duration of menstruation were both shortened after OC use, from 30.16 to 27.6 days and 4.74 to 3.65 days with Triella and from 30.49 to 27.6 days and 4.85 to 3.59 days with Adepal. Some diminution of menstrual flow was also observed. Spotting or staining was observed during 14.0% of days in the 1st cycle and 2.0% in the 6th cycle with Triella and during 11.9% of days in the 1st cycle and 3.9% in the 6th cycle with Adepal. Before treatment, during the 1st cycle, and during the 6th cycle respectively, 48.4%, 9.9%, and 4.8% of women using Triella and 65.5%, 11.4%, and 8.9% using Adepal experienced dysmenorrhea, while 45.1%, 12.1%, and 6.3% using Triella and 57.5%, 13.8%, and 10.7% using Adepal experienced premenstrual syndrome. There were no statistically significant changes in weight. Mean blood pressure did not show any tendency to increase with Triella after a temporary rise in the 1st 2 cycles, which was not statistically significant. Average blood pressure with Adepal increased from 118.6/70.9 before treatment to 121.4/71.6 in the 6th cycle. 3.3% of Triella users and 9.2% of Adepal users had blood pressure increases to 140/90 or above. Among cycles of Triella and Adepal use respectively, 6.9% and 8.3% had breast problems, 6.2% and 5.6% had digestive problems, 6.9% and 3.6% had abdominopelvic problems, 5.4% and 4.9% had headaches, 3.2% and 4.6% had leucorrhea, 1.9% and 3.6% had psychic problems, .9% and 1.5% had vascular problems, and .6% and .7% had skin problems. All side effects had a tendency to decline with use. No new anomalies were detected in the final gynecological examination, except a case of mastosis in an Adepal user. 20 Triella users and 23 Adepal users were evaluated before treatment and at the 3rd, 6th, and 12th cycle for triglycerides, fasting and postprandial insulin and glucose tolerance, and total cholesterol. There were no significant changes, although there were nonsignificant postprandial elevations in glucose and insulin with both formulations. There were slight declines in total cholesterol with both OCs. No pregnancies occurred in either group.