Physician assistants take on primary care duties that were once the exclusive domain of physicians. According to Kevin Lohenry, director of the Primary Care Physician Assistant Program at the University of Southern California, there are either 90,000 or 30 million reasons why someone might see a physician assistant rather than a physician. The 30 million is the number of Americans who don't have ready access to health care. He stresses that the crisis in primary care is even more acute today, and it's not just a function of money, but also the distribution of doctors by geography and specialty. Across the country, nurse practitioners and physician assistants can perform almost all of the duties previously carried out by primary care physicians. Nurse practitioners and physician assistants make up the largest number of clinicians within a growing group of advanced practitioners.