Background: Chronic pelvic pain (CPP) is a complex clinical scenario, which affects 15% of women. The published literature lacks a consistent definition of CPP. However according to Vercillini et al., CPP is defined by the duration and type of pelvic pain . CPP is present if the pelvic pain persists for more than 3 months duration and is constant or intermittent, cyclical or noncyclical in nature. Four types of pelvic pain have also been described and these include: cyclical pain during menstruation (dysmenorrhoea), deep dyspareunia, dyschezia and noncyclical pelvic pain. Therefore for the purposes of this study, CPP will be defined by these aforementioned types of pelvic pain and duration. Methods: Multi-centre randomised controlled trial comparing Mirena IUS versus expectant management in women with CPP and/or dysmenorrhoea who undergo laparoscopic surgery. All women aged 18 - 45 years with CPP scheduled for laparoscopy will be eligible for inclusion. Women with a non-gynecological cause of pelvic pain, contraindications to the use of Mirena IUS, previous hysterectomy, contraindications to laparoscopy and/or general anesthesia, use of hormonal treatment in the preceding three months, underlying gynaecological malignancies or known ovarian cysts other than endometriomata will be excluded. Importantly, all randomised women with endometriosis noted at the time of surgery will have the disease excised laparoscopically. Routine excision of endometriosis at laparoscopy will be performed according to the anatomical location and type (superficial or deep infiltrating endometriosis (DIE)). Women will be followed for up to 24 months after laparoscopic surgery. Results: The primary outcome measure is improvement of pelvic pain and/or of dysmenorrhoea post-laparoscopic surgery for women. Assuming a 30% reduction in pain for the expectantly managed group in order to detect a reduction in pain in the study group of 50% with an alpha of 0.05 and a beta of 0.20, the sample size was estimated at a minimum of 103 women per trial arm. Discussion: This trial will provide evidence to validate the effectiveness or otherwise of progestogen-releasing IUS in treating women with CPP who undergo laparoscopy surgery. The pros and cons of both trial arms will offer guidance to clinicians in making the right treatment choice.