Direct comparison
Co-Investigator vs. Sub-Investigator
Co-Investigator is a general research role; Sub-Investigator is FDA/ICH-defined (21 CFR 312.53), named on Form 1572 and the Delegation of Authority Log.
Written and maintained by CASRAI Editorial Board
Last updated
Ask CASRAI · free to try
Ask about Co-Investigator vs. Sub-Investigator
Ask your first 2 questions free below. Subscribers get 150 a day for $29 a month.
An AI assistant specialized in research administration. It cites the sources behind every answer, labels web answers and says when it can't answer.
Answers draw on CASRAI's guides and dictionary plus the federal and funder documents we index: Federal Register, Grants.gov, Regulations.gov and UKRI.
Works on this site and inside Claude, Cursor and the AI tools you already use.
Everything CASRAI publishes — this page, the dictionary, the guides and the news — stays free to read, with no account and no card.
How do Co-Investigator, Sub-Investigator compare side by side?
The table below compares Co-Investigator, Sub-Investigator across 7 procurement-relevant dimensions, from formally defined by clinical-trial regulation? through qualification/training documentation required?.
Side-by-side comparison
| Dimension | Co-Investigator | Sub-Investigator |
|---|---|---|
| Formally defined by clinical-trial regulation? | No — general collaborative-research term, used across grants, publications, and multi-institutional studies | Yes — 21 CFR 312.3 defines the role within the "investigator" framework |
| Named on FDA Form 1572? | Only if also formally serving as a sub-investigator | Yes, listed by name (does not sign the form) |
| Requires a Delegation of Authority Log entry? | Only if delegated protocol-critical trial tasks | Yes — task-level entries with start/end dates, per ICH E6(R2) 4.1.5 |
| Governing framework | Institutional and funder practice; no single regulatory definition | 21 CFR 312.53 / 312.60; ICH E6(R2) Section 4.1.5 |
| Applies outside clinical trials? | Yes — grants, non-trial collaborations, publications | No — a clinical-trial-specific designation tied to IND-regulated investigations |
| Who retains ultimate accountability? | Depends on the funder/collaboration structure | The PI, per 21 CFR 312.60, regardless of delegated tasks |
| Qualification/training documentation required? | Varies by institution/funder | Yes — CV/training/licensure records expected in the Investigator Site File to support each delegated task |
Common questions
Common questions about Co-Investigator vs Sub-Investigator
Is every sub-investigator also a co-investigator?
+
Informally, usually yes — most people functioning as sub-investigators are also described as co-investigators on the study team. But the reverse is not automatic: a co-investigator only becomes a sub-investigator once the PI formally delegates specific, protocol-critical trial duties to them, documented on the Delegation of Authority Log and, where applicable, listed on the FDA Form 1572.
Does a sub-investigator sign the FDA Form 1572?
+
No. Only the Principal Investigator signs Form 1572. Sub-investigators are listed by name on the form but do not sign it themselves.
Who is accountable if a sub-investigator makes an error?
+
The PI retains overall regulatory responsibility for the trial's conduct at that site under 21 CFR 312.60, even though a specific task was delegated to and performed by a sub-investigator. Delegation transfers performance, not the PI's accountability.
Does "Co-Investigator" mean the same thing on a grant as it does on a clinical trial?
+
Not exactly — the underlying idea (a substantively contributing researcher who is not the lead PI) carries over, but a clinical trial adds a regulatory layer (FDA/ICH requirements) that a non-trial grant collaboration does not have.
