Institutional Review Boards (IRBs) play a critical role in research, and assure safety and fairness to participants enrolled in research studies. Multisite studies are often reviewed by multiple IRBs (an IRB review at each site participating in the study), which can slow down study approval, result in duplication of effort, and occasionally produce contradictory decisions by different IRBs. To address these problems, the federal government has promoted the use of single IRBs (referred to as Central IRBs or CIRBs), where a single IRB is responsible for the review of all sites where the research study is conducted. The National Institutes of Health (NIH) has recently announced that beginning in 2017 all research conducted at multiple sites must be reviewed by a CIRB. This CIRB process is new and requires careful study to understand its pitfalls and benefits. As such, UMass Medical School and Columbia University received a (NIH) grant to study how different institutions conduct reviews of research involving multiple sites. A Spanish translation of this publication is available for download.