Headache, like back pain or abdominal pain, is a symptom that can have many causes. It can be a primary disorder, such as migraine or a tension-type headache. It may also be a symptom of an evolving intracranial disorder, such as an intracranial aneurysm or a brain tumor. Obtaining a complete and accurate history is important and necessary when examining a patient who is complaining of headaches and this takes practice. The important etiologies of sudden onset headache that need to be considered include a ruptured aneurysm with intracranial hemorrhage, subarachnoid hemorrhage, a hemorrhage into a mass or an arteriovenous malformation, arterial dissection and pituitary apoplexy. A 16-year-old teenager was admitted to our hospital because of an acute onset headache that was associated with vomiting. There was no other relevant history. He showed no abnormal physical and neurological signs. A brain computed tomographic scan showed a hematoma of right temporal lobe. In this case, an unexpected abrupt onset headache that had not occurred before was indicative of a potentially life-threatening secondary headache syndrome that required urgent investigation.