The diagnosis of median arcuate ligament (MAL) syndrome and its correlation with symptoms has been controversial since the disease entity was described. The authors describe a technique that will identify patients who will benefit from intervention. Eight patients with isolated celiac artery compression from MAL were identified by the authors. Their technique involved selective cannulation of the superior mesenteric artery (SMA) and injection of a vasodilator during angiography. Symptom reproduction and loss of collateral filling of the celiac territory represented a positive test: 4 of the 8 patients had a positive test and underwent successful surgical treatment of the condition; 3 of them remained asymptomatic at follow-up; 1 patient continues to have mild abdominal discomfort. Of the 4 patients with a negative test, 2 were found to have other conditions causing their symptoms. Vasodilator injection into the SMA is a useful diagnostic test to identify patients with symptomatic MAL syndrome.