BACKGROUND: Chronic pelvic pain affects ~15% of women, and is associated with 52 significant societal cost and impact on women’s health. Identifying factors involved in 53 chronic pelvic pain is challenging due to its multifactorial nature and confounding between 54 potential factors. For example, while some women with endometriosis have chronic pelvic 55 pain, there may be comorbid conditions that are implicated in the chronic pelvic pain rather 56 than the endometriosis itself. 57 OBJECTIVE: To explore multifactorial variables independently associated with the severity 58 of chronic pelvic pain in women. 59 STUDY DESIGN: Baseline cross-sectional data from an ongoing prospective cohort, 60 collected from patient online questionnaires, physical examination, and physician review of 61 medical records. Participants were recruited from a tertiary referral center for endometriosis 62 and chronic pelvic pain in Vancouver, Canada between December 2013 and April 2015. 63 Exclusion criteria included menopausal status or age > 50 years. Primary outcome was self- 64 reported severity of chronic pelvic pain in the last 3 months (0-10 numeric rating scale). 65 Potential associated factors ranged from known pain conditions assessed by standard 66 diagnostic criteria, validated psychological questionnaires, musculoskeletal physical exam 67 findings, as well as pain-related, reproductive, medical/surgical, familial, demographic and 68 behavioral characteristics. Mann-Whitney, Kruskal-Wallis, or Spearman test were used to 69 identify variables with an association with the primary outcome (p 0.05), followed by 70 multivariable linear regression to control for confounding and to identify independent 71 associations with the primary outcome (p 0.05). 4 Severity of chronic pelvic pain 72 RESULTS: Overall, 656 women were included (87% consent rate), of which 55% were 73 diagnosed with endometriosis. The following factors were independently associated with 74 higher severity of chronic pelvic pain: abdominal wall pain (p = 0.005), pelvic floor 75 tenderness (p = 0.004), painful bladder syndrome (p = 0.019), higher score on pain 76 catastrophizing scale (p 0.001), adult sexual assault (p = 0.043), higher body mass index (p 77 = 0.023), current smoking (p = 0.049), and family history of chronic pain (p = 0.038). 78 Severity of chronic pelvic pain was similar between women with and without endometriosis. 79 CONCLUSIONS: Multifactorial variables independently associated with severity of chronic 80 pelvic pain were identified, ranging from myofascial/musculoskeletal, urological, family 81 history, and psycho-social factors. Continued research is required to validate these factors 82 and to determine whether any are potentially modifiable for the management of chronic 83 pelvic pain.