This manuscript serves as a review of Mirena, the levonorgestrel intrauterine system (LNG IUS) as a very successful drug delivery system. The LNG IUS has a very high contraceptive efficacy rate, and low rates of patient discontinuation. In addition to its contraceptive benefits, most users experience a decrease in menstrual bleeding over the 5 years of use. LNG IUS has also been used for management of menorrhagia, dysmenorrhea, adenomyosis, and endometrial hyperplasia in some cases. The LNG IUS provides long term efficacy, high rates of compliance, rapid return to fertility, and minimal adverse effects during use.