This study aims to evaluate the effects of plasma beta endorphin level and exercise on migrainous headache. Forty patients with migrainous headache without aura (MWOA), firstly exercised on a treadmill and afterwards were asked to continue an aerobic home exercise program for six weeks. On evaluation, basal plasma beta endorphin level was negatively correlated with total duration of attacks in the last month period (P = 0.01). Exercise was found to have beneficial effects on all migraine parameters (P < 0.0001) and to increase beta endorphin levels after the treadmill practice (P < 0.0001) and after the home exercise program except four patients not regularly attended to the program (P < 0.0001). Any of the changes in headache parameters was not correlated with the change in beta endorphin level. However, pre-exercise beta endorphin level was found to be negatively correlated with the changes in the number of attacks (P < 0.05) and total duration of attacks (P = 0.01) and also with the change in beta endorphin level due to exercise (P < 0.0001). As a result, this study emphasizes the beneficial effect of exercise on migrainous headache, especially in patients with lower basal beta endorphin level.