A great deal of discussion and debate has surrounded the issue of autonomy of practice among physician assistants (PAs) and other non-physician clinicians. This study further explores this issue by closely examining the interactions between PAs and their supervising physicians in the provision of patient care. Utilizing a national sample of 1,112 full-time practicing physician assistants, PA-MD interaction patterns are measured and weighted in a scale as a proxy for autonomy of practice. Further, these measures are then used as the dependent variable in a regression analysis to better explain the dynamics between PA personal and practice characteristics and autonomy of practice. Overall, the tested model explained 29% of the variation in PA-MD interaction patterns. Independent variables that were particularly influential in the model were proximity to supervisor, clinical productivity, the percentage of PA patients treated using written clinical guidelines, specialty of practice, and practice setting.