Three-year fellowships will be awarded on a competitive basis to graduates of medical and graduate schools in the biological sciences holding M.D., Ph.D., D.V.M. or D.D.S. degrees. Awards will be based solely on the quality of the individual applicant's previous accomplishments, and on the merit of the proposal for postdoctoral research. Persons doing a second postdoc are eligible only if they are transferring to a different supervisor's laboratory and embarking on a new project not connected to their previous research. All U.S. citizens are eligible to apply with no geographic restriction on the laboratory of their choice. Foreign applicants will be eligible for study in U.S. laboratories. LSRF fellows must carry out their research at nonprofit institutions. LSRF fellows can change projects, laboratories, and/or institutions during the fellowship as long as the eligibility rules listed here are not violated. A person holding a faculty appointment is not eligible to apply for an LSRF fellowship. .