Principal Investigator and Sub-investigators

John Gregory Willis, MD graduate from Southwestern University in Georgetown, Texas and received his doctorate from Baylor College of Medicine. He completed his internship and residency at the Memorial Medical Center in Corpus Christi, Texas.

Dr. Willis is a specialist in Family Medicine and Board Certified by the American Board of Family Medicine. He is a member of the Texas Academy of Family Physicians, and the Texas Medical Association, and the American Academy of Family Physicians. He has served as president of the Williamson County Medical Society.

Dr. Willis is the Principal Investigator/Medical Director since 2006. He previously served as a sub-investigator from 2000-2005. Dr. Willis and his research staff have conducted numerous studies pertaining to cardiology, endocrinology including diabetes, pulmonary diseases (COPD and asthma), infectious diseases, vaccines, pain and pediatric pain medicine, obesity, urology, genitourinary, and gastroenterology.


Daniel Stephen Voss, MD received his undergraduate training at Texas A& M University and his medical degree from the University of Texas Medical Branch in Galveston, Texas. He completed his internship and residency in Family Medicine at the John Peter Smith Hospital in Fort Worth, Texas.

Dr. Voss is a specialist in Family Medicine and Board Certified by the American Board of Family Medicine. He is a member of the Texas Academy of Family Physicians, the Williamson County Medical Society and the Christian Medical and Dental Society. His special interests include family-centered Obstetrics and Pediatrics.


Florence Catherine Spitler, DO graduated from the University of Medicine and Dentistry - School of Osteopathic Medicine (UMDNJ-SOM) in 2001. Following her training, she accepted a position as Medical Director and Assistant Clinical Professor at UMDNY-SOM.

Dr. Spitler is a Board Certified Family Physician who opened her practice in Georgetown, Texas in September 2007. As a Family Physician, she provides compassionate medical care for newborns, children, adolescents, adults and seniors. Her services include annual well exams, vaccines, sports physicals as well as diagnosis and management of acute and chronic medical conditions. Her philosophy is to care for the whole person with an emphasis on body, mind and family dynamics. Dr. Spitler joined the medical staff at Georgetown Medical Clinic in March 2011 and has participated in clinical trials since that date.


Thomas Charles Bohmfalk, MD attended Rice University in Houston, Texas and received his medical degree from the University of Texas Southwestern Medical School at Dallas. He completed his internship and residency at John Peter Smith Hospital in Fort Worth, Texas and specializes in Family Medicine and is Board Certified by the American Board of Family Medicine.

Dr. Bohmfalk is a member of the American Academy of Family Physicians, the Texas Academy of Family Physicians, the Williamson County Medical Society and has been a member of the Georgetown Medical Clinic staff for thirty-nine years.


David Ryan Willingham, MD received his medical degree from Texas Tech University Health Science Center in Lubbock, Texas. His internship was completed at Baylor Scott & White Memorial Hospital in Temple, Texas.

His specialty is Family Medicine and he is Board Certified by the American Board of Family Medicine. He has been a member of the medical staff at Georgetown Medical Clinic since August 2016.