John Waller,1 Emma Sullivan,1 James Piercy,1 Christopher M Black,2 Sumesh Kachroo2 1Adelphi Real World, Manchester, UK; 2Center for Observational and Real-World Evidence (CORE), Merck & Co., Inc., Kenilworth, NJ, USA Objectives: We examined rheumatologists’ motivation for prescribing biosimilars, assessed their treatment preferences in relation to prescribing behavior and explored patient attitudes to biosimilars. Methods: Data were taken from the Adelphi Real World Biosimilars Programme, a real-world, cross-sectional study undertaken with German rheumatologists and patients with rheumatoid arthritis, ankylosing spondyloarthritis or psoriatic arthritis in 2015–2016. Rheumatologists provided data on their prescribing behavior and attitudes toward biosimilars and invited the next eight eligible consecutive consulting patients to complete a questionnaire. Rheumatologists were split into “investigative”, “conservative” and “other” groups. Results: Overall, 50 rheumatologists and 261 patients participated. Biosimilars accounted for 95% of rheumatologists would prescribe a biooriginator rather than biosimilar as the first- or second-line therapy if unrestricted. Patients showed some reluctance to accept biosimilars, and a small proportion of patients were unhappy when switched from a biooriginator to a biosimilar. Satisfaction with treatment was highest in patients who started treatment with a biooriginator prior to biosimilar availability. Patient concerns when starting treatment with a biooriginator or a biosimilar included not knowing enough about the drug (25%–41%), potential side effects (26%–32%) and potential long-term problems (19%–30%). Conclusion: Study results demonstrate that there is some reluctance from patients to accept biosimilars and the need to educate patients who are unsure to allow them to be involved in decision making, highlighting the importance of patient and physician communication. There remains a need for further research into nonclinical switching and the long-term impact of prescribing biosimilars. Keywords: biosimilars, rheumatology, autoimmune, patient acceptance, physician acceptance