Active members are physicians (DO and MD degrees) who have completed internal medicine training and hold a valid license to practice.

[6] Notable members include Karen J. Nichols, DO, MACOI, the first female president of ACOI and former medical school dean; Humayun J. Chaudhry, DO, MACOI, MS, president and chief executive officer of the Federation of State Medical Boards (FSMB) of the United States; and Robert A. Cain, DO, MACOI, president and CEO of the American Association of Colleges of Osteopathic Medicine (AACOM).

The recipient receives becomes a Fellow of the American College of Osteopathic Internists, which is abbreviated FACOI.

[11] The Gillum Society of Master Fellows was established in 1994 to honor fellows who have demonstrated outstanding past and present contributions to the College or to osteopathic internal medicine on a local, regional, or national level.

[16] The award is named for David Susser, DO, MACOI, a past president of ACOI, and cardiologist and former head of Internal Medicine at Botsford Hospital (Michigan).