Introduction Headache is one of the most common medical complaints. Many controversies exist regarding the nomenclature and classification of headache. The International Headache Society (IHS) developed and published a classification and diagnostic criteria in 1988. This classification system is cumbersome for day to day use. The IHS criteria are most useful for grouping patients for scientific purposes, such as clinical trials and epidemiologic studies. As many as 90 percent of all benign headache patients fall under a few categories of headache, including migraine, tension-type, and cluster headache. Physicians can easily become familiar with these common disorders and how to differentiate between them (table 1).