Study Objective: To evaluate continuance rates, bleeding patterns, and patient satisfaction with 52-mg levonorgestrel-releasing intrauterine system (LNG-IUS) use in adolescents and young adult women during the first 3 years of useDesign: We conducted an observational prospective study.Setting: Family Planning Service of a tertiary hospital in Brazil Participants: One hundred adolescents and young women aged 16-24 years.Intervention: Insertion of 52-mg LNG-IUS for the main purpose of contraception. Follow-up visits were conducted at 12, 24, and 36 months after insertion.Main Outcome Measures: Continuance rates, reasons for discontinuation of the method, and women's satisfaction and bleeding patternsResults: Among those who were not lost to follow-up, LNG-IUS continuance rates were 89.1% (82/92), 82.9% (72/87), and 75.3% (64/85) in the first, second, and third years of use, respectively. The main reason for discontinuation was acne, followed by expulsion of/malpositioned LNG-IUS. Other reasons for discontinuation were irregular uterine bleeding, dysmenorrhea, and abdominal pain. The amenorrhea rates were 50%, 54.1%, and 39% at 12, 24, and 36 months, respectively. Spotting rates increased during the first 3 years of use (20.8%, 16.7%, and 26.6%, respectively). Adolescents and young women using the LNG-IUS showed high rates of satisfaction, with 93.9%, 100%, and 96.8% of women being very satisfied/satisfied in the first 3 years of use. Only 2 participants who continued using the LNG-IUS reported being very dissatisfied/dissatisfied in the third year of follow-up.Conclusion: The LNG-IUS showed high rates of continuation and satisfaction in the first 3 years of use in Brazilian adolescents and young adults. Most women reported a favorable bleeding pattern.