Increasing evidence of the similarity between muscle contraction headache (MCH) and migraine has been reported. However, there seem to be some problems and confusion about the notion that MCH and migraine are similar. For clarification of the relationship of MCH to migraine, we carried out a series of multivariate analysis studies. One hundred and eighty headache patients (including 60 MCH patients, 60 combined headache patients and 60 migraine patients) were investigated. Clinical data of these 180 patients were analyzed using Hayashi's Quantification analysis and cluster analysis. It was possible to determine an MCH factor and a migraine factor from headache symptoms and characteristics. A diffuse and sequential distribution of patients was observed in the histogram of quantified symptoms with the purpose of discriminating headache categories. Thus, most headache patients might have both the MCH factor and the migraine factor in various proportions. We propose a slight modification of the headache severity model and add some development of the concept that MCH and migraine are a continuum. We submit a new headache model.