Umbilical arterial catheters (UAC) are routinely used in the care of critically ill newborns. Complications related to UACs include vascular compromise, hemorrhage, complications related to malposition, severance of the catheter itself, and infection. This article is Part II in a series dedicated to assessing infants with an umbilical catheter. Part I focused on infants with umbilical venous catheters; this article will focus on the physical assessment relevant to infants with an UAC. Complications related to UACs can occur during any phase of treatment: insertion, while indwelling, or after discontinuing the catheter. Review of clinical signs of complications along with clinical photographs, will assist caregivers in promptly recognizing UAC-related complications.