In two exploratory studies it was attempted to develop psychophysiological and self-report criteria for differentiating MCH and psychogenic headache. Subjects diagnosed as having muscle contraction headaches were assigned to low and high EMG groups following measurement of the frontalis muscle in a headache state. It was hypothesized that the low EMG group would display characteristics of psychogenic pain disorders. In the first study, nine subjects with high EMG, nine subjects with low EMG and nine control subjects participated. The results show that basal levels in a non-headache and headache state for the high EMG group were significantly different than the low EMG group, which were similar to control subjects. The low EMG group's self-report data were consistent with the hypothesis of a psychogenic disorder. The second study determined if changes in EMG activity across headache and pain-free states was a reliable effect by assessing frontalis EMG in three independent groups in two headache and two non-headache states. The results showed systematic changes in EMG in headache and non-headache states only for the high EMG group. These results suggest that accurate classification of headache disorders may alleviate some of the contradictory data in the headache literature.