It was the objective of this study to explore the possibility that the aggregation of red blood cells is enhanced in individuals with increased intracranial hypertension (IIH). This is a prospective cross sectional examination in a cohort of patients with IIH and matched controls. The aggregation of red blood cells in the peripheral venous blood was determined by using a slide test and image analysis. We have presently included a group of 33 women with IIH and the same number of women matched for age, body mass index, vascular risk factors and medications. A significant (p = 0.038) increment in fibrinogen concentrations was noted in the patients (341 +/- 60.8 mg/dl) as opposed to the controls 307.9 +/- 64.8). The same stands for the aggregation of red blood cells (aggregation parameter of 8.7 +/- 4.9 in patients vs.5.9 +/- 3.2 in the controls, p = 0.001). We noted an increment in the aggregation of red blood cells in the peripheral blood of 33 women with IIH as opposed to matched controls. Being associated with capillary slow flow, these findings might be relevant to the ethiopathogenesis of this disease.