An issue of concern for dermatologists may be ACOs’ potential effect on referral patterns. At least within Medicare ACOs, patients can continue to see any physician of their choice. They are not limited to seeing providers in the ACO. Therefore, patients who already have an established relationship with a dermatologist can continue to see that dermatologist. However, for patients who seek referrals for dermatological care, physician participants in ACOs will likely encourage their patients to see dermatologists with whom they have good working relationships and likely those who are within the referring physician’s ACO.