Purpose: A rapidly increasing use of biological drugs has led to substantial costs. Shift to biosimilars enables considerable reduction of these costs without jeopardizing the treatment of patients, but most countries have extensive possibilities of untapped cost-savings. The aim of this study was to describe the Danish quick and near-complete implementation of the two first TNF inhibitor biosimilars (infliximab and etanercept). Methods: We shed light on the considerations and experiences made during the implementation, and present key figures from the implementation. Results: The infliximab biosimilar constituted 90.6% of the total amount of infliximab four months following patent expiration of the biooriginator. Similar results were seen for etanercept biosimilar. Substantial cost reductions were experienced in the way that e.g. the infliximab-shift reduced cost by two thirds. Conclusion: We believe that a thorough preparation and an organizational setting supporting the implementation is crucial for the successful implementation. This same implementation model will be used for future biosimilars.