The transdermal contraceptive patch delivers ethinyl estradiol and norelgestromin (17-deacetylnorgestimate) at a rate over seven days that results in efficacy paralleling that achieved with oral contraceptives. Due to the pharmacokinetics of the system, adequate steroid levels are maintained for two days beyond the recommended duration of use of an individual patch, with resulting maintenance of efficacy. With perfect use, the failure rate is 0.70 pregnancies per 100 woman-years and for typical use, the rate is 0.88 pregnancies per 100 woman-years. Body weight above 90 kilograms (198 pounds) is associated with lower efficacy. Cycle control is similar to that achieved by oral contraceptives. With the exception of a transient increase in breast tenderness, the side effect profile is similar to that noted by oral contraceptive users. A major advantage of this method compared to oral contraceptives is a nearly 90% perfect adherence to the dosing schedule across all age groups. Partial or total detachment of the patch occurs at an overall rate of 3.8%. This rate is not affected by warm humid climates, vigorous exercise, or exposure to saunas or water baths.