OBJECTIVES: To evaluate the budget impact to a health plan after introducing dienogest (2 mg) as a treatment option for endometriosis-associated pelvic pain (EAPP) patients. METHODS: The analysis was conducted from a German payer’s perspective over a five-year time horizon. The budget impact model (BIM) specifically considered women with EAPP. This included women with newly diagnosed endometriosis and women who have previously failed other medical treatment for EAPP. A recently developed cost-effectiveness (CE) model for endometriosis provided the estimates of average treatment duration. This CE model compared different treatment pathways for women with EAPP and used a 50% improvement in pelvic pain as a definition of a treatment responder to elicit treatment duration. After combining epidemiological data, market uptake assumptions from market research forecasting, and current GnRH-a drug treatment costs, and average treatment duration, the BIM estimated the incremental budget impact after adopting dienogest as a treatment option at the expense of GnRH-analogues. The model assumed that during the first year, 5% of EAPP patients receive dienogest at the expense of GnRH-analogues. After 5 years, it was assumed that dienogest would capture 15% of the EAPP market. A plausible range of parameter values were considered in the sensitivity analysis. RESULTS: In the hypothetical health plan approximately 0.54% of members were estimated to be diagnosed with EAPP and receiving medical intervention. In the year after introduction of dienogest, the overall budget used to treat EAPP was estimated to decrease by up to 4% with the budget saving estimated to increase to around 11.0% by Year 5. CONCLUSIONS: In patients with EAPP, the budgetary impact of adding dienogest to a health plan, in Germany, at the expense of the GnRH-analogues was estimated to result in a budgetary cost saving.