Absence of an internal jugular vein at birth is infrequent. These developmental anomalies affect approximately 0.05 percent to 0.25 percent of the population in the general community. Avascular abnormalities emerging from the internal jugular vein were detected during radiographic studies of chronic headache in an adult male patient. A dull headache troubled a 32-year-old man for more than 20 years. After taking most of NSAIDs and other medications for the condition, which persisted, a diagnosis of left internal jugular vein agenesis was made, which was most likely the cause of the headaches. When treating recurrent, persistent headaches in the emergency room and outdoor medical services, keep in mind that agenesis of the jugular venous system can play a role-one of the uncommon causes of headaches we have observed in our cases.