In evaluating a headache patient, the first task is to identify or exclude secondary headaches based on the history, and the general medical as well as neurological examinations. Physical and neurological examinations are mandatory, overall in emergency room setting. If suspicious features are present, diagnostic testing may also be necessary. Once secondary headaches are excluded, the task is then to diagnose one more specific primary headache disorder. We summarize some typical emergency room situations in which headaches must be differentiate and treated.