The 99th Medical Group is comprised of approximately 1,600 personnel who are dedicated to providing preventive, emergency and acute care services for approximately 11,000 active-duty members and their dependents. Health care services are also provided directly or coordinated for over 49,000 retirees, their dependents or other eligible beneficiaries on a space-available basis.

Members of the 99th MDG operate a 50-bed medical center and are also part of a collaborative joint venture with the Department of Veterans Affairs addressing 78,000 DoD and VA beneficiaries healthcare needs.

The Mike O'Callaghan Military Medical Center (MOMMC) -- general information number (702) 653-2273 -- opened August 1994 and now provides the following services: aerospace medicine, allergy, anesthesia, audiology, blood bank, cardiac cath lab, cardiology, cardiopulmonary, colorectal surgery, critical care unit, dental, dental specialties, dermatology, dialysis-acute, emergency department, endocrinology, family advocacy, family medicine, gastroenterology, health promotions, hematology, immunology, infectious disease, inpatient medical/surgical, inpatient obstetrics, internal medicine, laboratory, nephrology, neurology, nuclear medicine, nutritional medicine, occupational medicine, oncology, ophthalmology, optometry, orthopedics, otolaryngology, pain management, pastoral care, pathology, pediatrics, pharmacy, physical exams, physical therapy, plastic surgery, podiatry, psychiatry, psychology, public health, pulmonary, radiology, respiratory therapy, rheumatology, same day surgery, social work, surgery, ultrasound, urology, vascular surgery, women's health and wound care clinic.