Maddox's career has focused on healthcare equity for minorities, women, and children, in both the United States and abroad.[8][9] She first started working in 1965 as a blood bank technician in the Department of Medicine at the Medical College of Virginia.[4][5] From 1968 to 1985, she worked as a researcher, instructor, and visiting scientist in various institutions including the Department of Inhalation Toxicology, the Department of Ophthalmology at the Washington Hospital Center, the Department of Biology at American University,[10] the Department of Physiology and Biophysics at Georgetown University Medical Center,[11] the French Atomic Energy Commission,[12] and the Department of Physiology and Biophysics at Georgetown.[6]