We describe an assessment of the collective impact of 35 grants that the Howard Hughes Medical Institute (HHMI) made to biomedical research institutions in 1999 to support precollege science education outreach programs. Data collected from funded institutions were compared with data from a control group of institutions that had advanced to the last stage of review but had not been funded. The survey instrument and the results reveal outcomes and impacts that HHMI considers relevant for these programs. The following attributes are considered: ability to secure additional, non-HHMI funding; institution buy-in as measured by gains in dedicated space and staff; enhancement of the program director's career; number and adoption of educational products developed; number of related publications and awards; percentage of programs for which teachers received course credit; increase in science content knowledge; and increase in student motivation to study science.