This award provides ongoing support to The Jackson Laboratory, a private, non-profit research institution, to continue their Research Experience for Undergraduates Site. Undergraduate science students with exceptional ability have been participating as research apprentices since 1929 at The Jackson Laboratory, . Twelve undergraduates, selected from 300 applicants nationwide, are exposed to all aspects of the research process by conducting hands-on, basic research in mammalian genetics for 10 or 12 weeks in the summer under the sponsorship of staff scientists. The students' projects are components of their sponsors' independent, investigator- initiated research programs. Inbred and mutant laboratory mice are utilized in many projects. All students are from outside the host institution; about half are from baccalaureate colleges. Students with diverse science preparations are accepted, with each participant's project tailored to his or her background . Students' work at the bench is supplemented by group sessions on careers, ethics, critical scientific thinking, and a formal student symposium. Follow-up activities, including affiliations with graduate schools, foster the students' continuing participation in science. 100% of the REU participants who have graduated are now in graduate or medical school or are employed in science. Long-term studies of program alumni show that a very high percentage receive doctoral degrees in the biological sciences or medicine.