In the present study, resting EMG levels were measured bilaterally in the frontalis and temporalis muscles in muscle contraction headache, migraine, and mixed muscle contraction-migraine headache patients and in healthy control subjects. Besides absolute EMG levels, proportional EMG levels were obtained by relating the absolute EMG amplitude to the EMG amplitude during maximal contraction. The headache-free state, a state of relatively weak headache, and a state of relatively strong headache were examined. The data of the three patient groups were pooled because significant differences between the groups were absent. Absolute EMG levels in the patients during the headache-free state were not significantly different from those of the controls except for the right frontalis muscle where the patients showed significantly higher levels than the controls. Proportional EMG levels, however, were for all muscles significantly higher in the patients group. Maximal EMG levels were generally significantly lower in the patients than in the controls. In the patients group, both absolute, proportional, and maximal EMG levels were in most cases not significantly different between a state of relatively weak and a state of relatively strong headache. The significance of these findings with respect to the generation of head pain is discussed.