A mass departure of Ph.D.-level scientists and health researchers has hollowed out 14 federal research agencies, producing a net loss of more than 4,200 positions over the past year. Science’s analysis of White House OPM data shows retirements and resignations—rather than mass firings—drove exits at agencies including the NIH and NSF. The shifts follow the Trump administration’s budget proposals and program cuts that chilled hiring and ended rotator appointments. The loss was most acute at the NIH, which saw departures surge from 421 in 2024 to more than 1,100 in 2025. NSF lost nearly 40% of its pre‑Trump Ph.D. workforce as rotator roles disappeared. University researchers and federal rotators have been a key pipeline into federal labs; their removal threatens grant review, program continuity and university–agency collaboration. Higher education leaders and research universities told Science and Inside Higher Ed that abrupt grant suspensions and regulatory uncertainty are forcing faculty and postdocs to choose private‑sector roles or domestic university posts. The exodus raises immediate operational risks for federally funded research and longer-term concerns about the U.S. research workforce and graduate training pipelines.