• Temporal muscle blood flow was measured with the xenon 133 clearance technique in 40 patients with chronic tension-type headache and in 13 control subjects. Pressure-pain threshold in the temporal region was determined with an algometer. Patients and control subjects did not differ in any of the blood flow parameters. Resting blood flow at the two sides was highly correlated (Spearman coefficient, r =.61) and no right/left differences could be demonstrated. In both patients and control subjects, blood flow increased approximately fivefold during isometric work (1/3 of a maximum surface electromyogram). Reactive hyperperfusion after isometric work was found in 8 patients and in 1 control subject. There was no definite correlation between the pressure-pain threshold and the corresponding blood flow. It is not likely that temporal muscle ischemia is the cause of muscle tenderness and pain in patients with chronic tension-type headache.