Priapism is defined as persistent penile erection continuing beyond, or unrelated to, sexual stimulation. Proper diagnosis encompasses at least 2 very different pathophysiologic processes. Ischemic priapism ("low flow") is a disorder of venous outflow and/or stasis. Nonischemic priapism ("high flow") is a disorder of arterial flow. We present 2 cases that review each condition. The first case highlights a 32-year-old man with a medical history of sickle cell disease who presented to the emergency department complaining of a persistent, painful erection that had continued for 18 hours. The second case describes a 24-year-old man with no significant medical history who sustained trauma to his pelvis while skateboarding. Although the initial evaluation of both types of priapism is similar, pathophysiology and resulting interventions differ for each, underscoring the importance of proper diagnosis.