Biologics prescribed by rheumatologists and gastroenterologists are among the most commercially successful biopharmaceutical products in the world. These biologics are a prime target for biosimilar developers. In February 2015, EU5 rheumatologists and gastroenterologists gained access to the first biosimilar licensed for use in their specialties, and we forecast that over the coming decade the immune biosimilar space will grow rapidly as further biosimilars are approved in Europe, the United States, and Japan. For biosimilar marketers looking to secure a foothold in this future market, understanding the perceptions and expectations of these specialists with regard to biosimilars is paramount. We conducted primary market research with rheumatologists and gastroenterologists in the United States and Europe to understand their perspectives on biosimilars and their expected adoption rates. Based on our extensive market research, this report also provides highly granular brand and biosimilar market forecasts for the United States, Europe, and Japan.