Fluoroscopically guided, contrast-enhanced epidural steroid injections (ESIs) are frequently performed for radicular symptoms. Interventionalists performing these procedures should have a thorough and detailed understanding of spinal anatomy to safely and effectively deliver the desired injectate to the targeted site. Being able to differentiate epidural from nonepidural contrast flow is vital as is recognizing flow to undesired locations. This article summarizes the characteristics that distinguish between ideal epidural flow patterns and nonideal subarachnoid, intradural, and other suboptimal contrast flow patterns. Recognizing these patterns is essential for safe and successful ESIs and to prevent avoidable complications.