Extramural Medical Officers serve as consultants and clinical investigators in their area of expertise. They use their medical expertise to administer extramural research grants and/or contracts in a major program area. In the area of assigned responsibility, Extramural Medical Officers work diligently to evaluate activities of funded investigators and make recommendations regarding the contribution of the research to the goals and objectives of the program.

Intramural Medical Officers serve as primary investigators or project members for research projects of broad and complex scopes to treat problems that are exceptionally difficult. The Medical Officers' major duties are to develop a research program that will enhance their laboratory's research goals and objectives, keep abreast of scientific and clinical developments, and analyze, evaluate, and interpret scientific and clinical data in order to prepare papers for publication and present findings at seminars and scientific meetings.