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Comparing Popular Research Project Grants—R01, R03, and R21

This page discusses the three most common types of Research Projects (R): the NIH standard independent R01, the smaller R03, and the exploratory/developmental research R21 activity codes.

For other types of grants, check Types of Funding Opportunities.

We strongly advise you to contact an NIAID program officer before you start to develop your application. He or she can advise you on whether your proposed project is appropriate for a particular grant type.

The main driver of your decision for one activity code over another should be the scientific scope of the work being proposed. Normally, R01-type projects are mature ideas with preliminary data supporting a hypothesis. R21 projects are usually high-risk/high-reward and require a high degree of innovation. R03 projects are usually descriptive and are used to generate hypotheses and data to support them.

Is an R01 Right for You?

An R01 is for mature research projects that are hypothesis-driven with strong preliminary data. R01s provide up to five years of support, with a budget that reflects the costs required to complete the project.

If you have strong preliminary data supporting your hypothesis, we recommend applying for an R01. For more on qualifying for an R01, refer to Determine Eligibility for NIAID Grants.

New investigators, when trying to determine whether submitting an R01 application is a good idea, consider the following:

  • Do you have strong preliminary data that support your hypothesis/hypotheses?
  • Is there a strong rationale for the proposed study?
  • Do you have a proven track record of experience in the field, including publications in scientific journals?
  • Do you or your collaborators have sufficient expertise to accomplish the goals of the proposed work?

Read Know Your Audience and Write Your Research Plan for more information about writing your application.

Reviewers are asked to consider that new investigators may have a more modest track record and publication record than established investigators. Peer reviewers are advised to look more at your potential than your past achievements. Also note that NIAID new investigators benefit from a more favorable payline for R01 applications.

For additional details, check Information for New Investigators.

Smaller Awards (R03, R21)

If your project is not ready for an R01, you can consider a two-year small grant (R03) or exploratory/developmental research grant (R21) to generate preliminary data or develop approaches that could support a hypothesis that can be tested under the R01 activity code. If you are considering either of these activity codes, get more advice from a program officer before applying.

R03 Is Small

Don't let the word "small" fool you into thinking that an R03 is especially easy to get; it's not. Like most other grant activity codes, your application will have stiff competition, will undergo peer review, and must be suitable for the activity code.

Your project must be tightly focused, able to be completed in two years, and manageable with a maximum of $100,000 in direct costs over the two-year period. If your project doesn't meet these criteria, it's not likely to be well received by reviewers.

Examples of projects that fit the R03 include:

  • Pilot or feasibility studies
  • Surveys
  • Descriptive studies
  • Secondary analysis of existing data
  • Small, self-contained research projects
  • Adaption or further development of research methodology or new research technology

To see the type of projects that have been funded, go to NIH RePORTER and select R03 in the Activity Code field. Also refer to R03 Sample Applications and Summary Statements.

New Investigators: R03 Might Not Be Your Best Option

At first glance, the R03 seems well suited to a new investigator. You can request up to $50,000 a year in direct costs and do not need preliminary data. And for someone who's never written a grant application, the shorter six-page Research Strategy (versus 12 pages for an R01) might be appealing.

That said, however, the smaller page limit means you need a concise, tightly focused research plan. The short time provided to complete the project and the limited budget mean you have little room for course correction.

Thus, when considering the R03 activity code, be sure to think about the scope of the research you are proposing, paying special attention to the timeline of the project and the funds that will be needed to complete the project.

Should You Apply for an R21?

The R21 activity code is intended to encourage exploratory/developmental research by providing support for the early and conceptual stages of project development. NIH has standardized the exploratory/developmental grant (R21) application characteristics, requirements, preparation, and review procedures in order to accommodate investigator-initiated (unsolicited) grant applications.

R21 projects are usually highly innovative driving the high-risk/high-reward principle that is characteristic of this activity code. R21 awards are intended to allow short duration funding (two years) for innovative ideas. R21 projects should be distinct from those supported through the traditional R01 and are not intended as a bridge between training and obtaining an R01 grant.

Here we lay out some considerations you'll want to pay attention to if you're thinking about submitting an R21 application.

R21 Pros and Cons


  • Allows you to introduce novel scientific ideas, model systems, tools, agents, targets, and technologies that have the potential to substantially advance biomedical research.
  • Preliminary data are not required for an R21 application.


  • If you're applying for an R21 to generate preliminary data, you could end up coming up short for time with a two-year grant.
  • If you mis-use the R21 activity code to support a small R01-type research project, you may find that two years is not long enough to complete a hypothesis-based project that yields enough data for publication or generates sufficient preliminary data for an R01 application.
    • In addition, the purpose of the R21 activity code is not necessarily to support hypothesis-based research.
    • Further, your R21 won't benefit from our higher R01 payline for new and early-stage investigators.

For a comparison of several key characteristics of R21s and R01s, see the next section.

R21 or R01?

This table compares some features of the parent R21 and R01 fund opportunity announcements (NOFOs). Note that institutes may publish their own funding opportunities (initiatives) using the R21 or R01 activity codes with different characteristics.

CharacteristicParent R21Parent R01
PurposeTo introduce novel scientific ideas, model systems, tools, agents, targets, and technologies that have the potential to substantially advance biomedical research.To support a discrete, specified, circumscribed an area representing the investigator's specific interest and competencies, based on NIH's mission.
DurationUp to two years.Up to five years.
BudgetUp to $275,000 in direct costs over two years. At most $200,000 for any year.No limit (But note that applicants must request Division permission to submit grants with budgets of $500,000 or higher for any year of the grant. Check our Big Grants webpage and Big Grants SOP.)
Preliminary dataNot required.Required.
ParticipationFor a list of participating institutes and centers (ICs), check the parent R21 announcements on our Funding Opportunities page.Most NIH ICs. For a list of participating ICs, check the parent R01 announcements on our Funding Opportunities page.
New Investigator benefitsNot ApplicableHigher payline than established PIs.
NIAID success rate for FY 2018*21.5 percent22.1 percent

* Data come from RePORT's Research Project Success Rates for NIAID.


No matter which funding opportunity you choose, you are advised to discuss with your program officer to make sure you are applying to the appropriate NOFO. Also, you need to consider where your financial support will come from should you have a funding gap while awaiting receipt of an NIH award. Read more in Approaches for Staying Funded.

To find information about different activity codes, go to NIH's Types of Grant Programs page.

Have Questions?

A program officer in your area of science can give you application advice, NIAID's perspective on your research, and confirmation that NIAID will accept your application.

Find contacts and instructions at When to Contact an NIAID Program Officer.

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