It has been suggested that low tension glaucoma (LTG) could be the consequence of a hemodynamic crisis or chronic occlusive disease. The purpose of the present study was to test this hypothesis by comparing three groups of patients matched for age and sex: 51 patients with LTG, 51 patients with open angle glaucoma (OAG) and 46 control patients. Clinical symptoms and history of occlusive arterial disease and conditions which could be associated with or were the consequence of acute blood pressure lowering were not more frequent in the LTG group. The prevalence of rhythm and conduction abnormalities on the ECG was two times more frequent in the glaucoma groups, but the differences were not statistically significant. Mean cardiovascular risk factor levels were not higher in the LTG group than in the two other groups. But the mean difference of blood pressure between the standing and lying positions was significantly greater in the LTG group (systolic blood pressure: -6.9 mm Hg) than in the OAG group (-1.2 mm HG) and the control group (-1.5 mm Hg). These results suggest that postural hypotension could play a role in the pathogenesis of LTG.