Many granting agencies allow reviewers to know the identity of a proposal's principal investigator (PI), which opens the possibility that reviewers discriminate on the basis of PI race and gender. We investigated this experimentally with 48 NIH R01 grant proposals, representing a broad range of NIH-funded science. We modified PI names to create separate white male, white female, black male and black female versions of each proposal, and 412 scientists each submitted initial reviews for 3 proposals. We find little to no race or gender bias in initial R01 evaluations, and additionally find that any bias that might have been present must be negligible in size. This conclusion was robust to a wide array of statistical model specifications. Pragmatically, important bias may be present in other aspects of the granting process, but our evidence suggests that it is not present in the initial round of R01 reviews.