Two kinds of edema have been observed in patients subject to vascular headache of the migraine type. One was a localized fluid accumulation that developed during the headache and occurred primarily in those scalp areas in which headache was experienced. This was featured by tenderness and slight to moderate pitting. The second was a more generalized fluid accumulation that commonly developed before the headache, involved many parts of the body, and was demonstrable by weight gain and pitting of dependent body areas. Data about the latter type were recently analysed by Schottstaedt and Wolff,1who indicated that headache and widespread fluid retention were often concomitant but not causally related phenomena. Their data showed that there was frequently a retention of sodium, potassium, and water before the headache and a diuresis during the phase of dwindling intensity of the headache. The present studies were undertaken to determine the frequency, magnitude,