Objective: To investigate the prevalence and experience of symptom flares in women with Chronic Pelvic Pain (CPP) as well as their triggers Design: Cross-sectional questionnaire within the Translational Research in Pelvic Pain clinical cohort study. Setting: Women with CPP, with subgroups of women with endometriosis (EAP), interstitial cystitis/bladder pain syndrome (BPS), comorbid endometriosis and interstitial cystitis/bladder pain syndrome (EABP), and those with pelvic pain without endometriosis or interstitial cystitis/bladder pain syndrome (PP). Population or sample: 100 participants across subgroups. Methods: Questionnaire within large cohort study. Main Outcome Measures: The prevalence and characteristics of short, medium and long symptom flares in CPP. Results: 76% of women with CPP experience symptom flares of at least one length (short, medium and/or long). Flares are associated with painful and non-painful symptoms. There is large variation amongst those with CPP for the frequency, duration, symptoms and triggers for these flares. Participants reported flares as stopping them from doing things they would usually do, participants thinking about symptoms of flares as well as flares being bothersome. Conclusions: Flares are prevalent and clinically very important in the context of CPP. More research is needed to elucidate the mechanisms and characteristics underlying flares. Clinical practice should include an enquiry of flares with the aim of finding strategies to lessen their burden. Funding: This project has received funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 777500. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme and EFPIA Companies.