Purpose of ReviewBiosimilars of the reference biologic therapeutics infliximab, etanercept, adalimumab, and rituximab are entering the market. Clinical and real-world data on the effects of reference → biosimilar switching are limited. This review was carried out to assess the current body of switching data.Recent FindingsFifty-three switching studies were identified. Infliximab publications covered CT-P13 (25 studies), SB2 (1), infliximab NK (1), and unspecified infliximab biosimilars (2). Etanercept publications covered SB4 (2) and GP2015 (2). Adalimumab publications covered ABP 501 (2) and SB5 (1). Rituximab publications covered CT-P10 (1). Efficacy and safety data generally showed no differences between patients who switched treatments versus those who did not. No differences were seen pre- and post-switch. Immunogenicity data were presented in 19/37 (51%) studies.SummaryAdditional data from switching studies of these therapies are still required, as is continuing pharma-covigilance. Switching should remain a case-by-case clinical decision made by the physician and patient on an individual basis supported by scientific evidence.Electronic supplementary materialThe online version of this article (doi:10.1007/s11926-017-0658-4) contains supplementary material, which is available to authorized users.