This guidance is intended to assist clinical investigators, sponsors, sponsor-investigators,2 and institutional review boards (IRBs) in determining whether research studies involving human subjects must be conducted under an investigational new drug application (IND), as described in title 21 of the Code of Federal Regulations, part 312 (21 CFR part 312) (the IND regulations). This guidance describes when an IND is required, specific situations in which an IND is not required, and a range of issues that, in FDA’s experience, have been the source of confusion or misperceptions about the application of the IND regulations.3 This guidance addresses only whether an IND is needed. If your study also involves the use of a device, you should determine whether such use is subject to 21 CFR part 812 (the IDE regulations).