To investigate the impact of placement in the procedures of gynecological laparoscopies or routine placement on the effects of levonorgestrel-releasing intrauterine system (LNG-IUS) for symptomatic adenomyosis in a prospective cohort study. From December, 2006 to December, 2014, patients with adenomyosis diagnosed by transvaginal ultrasound in outpatient or inpatient clinics of Peking Union Medical College Hospital received the treatment of LNG-IUS.Before and after placement of LNG-IUS all the parameters were recorded including carrying status of IUS, symptoms and scores of dysmenorrhea, menstruation scores, biochemical indicators, physical parameters, menstruation patterns and adverse effects.Impact of placement timing (in the procedures of laparoscopies vesus routine placement) on the treatment effects, menstruation patterns and adverse effects of LNG-IUS were analyzed. 1 100 patients meet the inclusion criteria, with median age 36 years (20-44 years), median follow-up 35 months (1-108 months), of which 385