Current classification systems for diagnosing recurring headaches utilize sets of specific criteria. To determine the usefulness of these criteria in the practical application of diagnosing headache patients, 698 headache specialists were asked to review four case vignettes of headache patients and assign a diagnosis. They also ranked International Headache Society (IHS) criteria along with other features commonly used in the diagnosis of headaches in order of importance. There was no difference in ranked importance for the specific criteria posed by the IHS compared with commonly used criteria not included within the IHS system. A large majority of the respondents combined IHS features with other associated features not used in the IHS system as the basis of diagnostic assignment. These results raise a question about the acceptance and utilization of the IHS system as a basis for diagnoses. They also suggest that there is a need to educate health care providers about the appropriate use of the current IHS criteria to increase reliability of headache diagnosis.