Background: Basic simulation training in endourology was established with the endoscopic stone treatment step 1 (EST-s1), which is now recognized worldwide for training and examination. Following on from EST-s1, the endoscopic stone treatment step 2 (EST-s2) was started by the European Association of Urology (EAU) sections.Objective: We describe the methodology used in the development of EST-s2 assessment curriculum. Materials and Methods: The ''full-life cycle curriculum development'' template was followed for curriculum development, focusing on intermediate training of EST protocol with complex endourologic tasks. A cognitive task analysis (CTA) was run in accordance with EAU Urolithiasis guidelines. The protocol and its details underwent a first consensus by Delphi method with EAU Urolithiasis Section experts in March 2017. Once the outcome and metrics were decided, curriculum development was carried out. Purpose-built stones were developed, and simulator system requirement was defined. Preliminary testing was done in European Urology Residents Education Programme 2019 and in phase five the protocol was finalized with full tutor instruction sheet. Results: The EST-s2/A curriculum development took 38 months and involved EAU Uro-technology and urolithiasis sections with coordination from the European School of Urology training group. Starting from the initial CTA, a 1277-word revision with preliminary task description was produced. Nine intermediate skills were identified and included in the final training protocol. The training content and session evaluations were carried out by 26 experts and 16 final year trainees, respectively. Although the experts agreed that EST-s2/A protocol was well structured (96%), covered the complex endourologic maneuvers (92%), and was useful to optimize and improve hands-on-training (HoT) sessions (92%), the overall evaluation was scored 4.25/5 by trainees.