SYNOPSIS The purpose of this study was to test the effect of muscle contraction headache chronicity on electromyographic (EMG) response. Frontal EMG was measured under two stress conditions and three baselines for subjects complaining of muscle contraction headaches for (1) 3 19 years, (2) £ 10 years, and (3) subjects not complaining of headaches of any kind. There were ten subjects in each group. The three groups were equivalent in age and sex distribution. They did not differ in their ratings of the stressfulness of the experimental conditions. Neither ANOVA nor ANCOVA with frequency of headache as the covariate supported Group differences or Group X Trials interactions. The results do not support the hypothesis that changes in frontal musculature occur as a function of the number of years that an individual has had a problem with muscle contraction headaches. The results are consistent with those of other EMG investigations employing an adaptation period of 3 5 minutes. They are also supportive of the recent skepticism about frontal EMG biofeedback as a critical component in the treatment of muscle contraction headaches.