Introduction: To compare all-cause and endometriosis-related healthcare resource utilization (HCRU) and healthcare costs by service categories (outpatient, inpatient, emergency room [ER], pharmacy) among patients with newly diagnosed endometriosis using opioids compared to patients with endometriosis not using opioids. Methods: A retrospective analysis of IBMÒ MarketScanÒ Commercial Claims data from 2009 to 2018 was performed for women aged 18-49 with newly diagnosed endometriosis (International Classification of Diseases (ICD)-9 code 617.xx; ICD-10 code N80.xx) over 24 months follow-up. Patients were stratified on the basis of opioid use within 12 months post first endometriosis diagnosis date. Patients with opioid use were 1:1 matched to patients without opioid use using propensity score matching. Results: A total of 85,329 female patients with a new endometriosis diagnosis were identified and 48,470 patients (24,235 opioid and 24,235 non-opioid users) remained after inclusion-exclusion criteria and matching. Opioid patients had an estimated mean 30.33 outpatient visits, 29.59 pharmacy fills, 0.28 inpatient visits, 0.65 ER visits, and total length of stay (LOS) was 1.01 days. Non-opioid patients had an estimated mean 27.94 outpatient visits, 22.06 pharmacy fills, 0.23 inpatient visits, 0.42 ER visits, and total LOS was 0.82 days. On average, opioid patients had significantly greater allcause HCRU compared to non-opioid patients (all p \ 0.0001). Among endometriosis-related healthcare utilization, there were similar ER visits, but lower outpatient visits, inpatient visits, and total LOS and higher pharmacy fills among opioid and non-opioid patients. Estimated mean all-cause costs were higher among opioid ($26,755) vs. non-opioid ($19,302) users (p \ 0.0001). A similar trend was observed for estimated mean endometriosis-related costs. Conclusion: This analysis observed significantly higher all-cause HCRU and costs for opioid users compared to non-opioid users Digital Features To view digital features for this article go to