We measured blood flow in the finger in 38 control subjects with normal ocular findings without migraine, 13 control subjects with normal ocular findings with classic migraine, 17 patients with low-tension glaucoma with classic migraine, and 29 patients with low-tension glaucoma without migraine. Three blood flow measurements were recorded: one at baseline, one after immersion in warm water (40 C), and one after ten seconds' exposure to cold water (4 C). The mean baseline flow and the mean flow after exposure to cold was lower in patients with low-tension glaucoma (P = .013 and P less than .001, respectively).