Administration of low doses of Escherichia coli endotoxin (LPS) to humans enables the study of inflammatory mechanisms. The purpose of the present study was to investigate the retinal vascular reactivity after LPS infusion. In a randomized placebo-controlled cross-over study, 18 healthy male volunteers received 20 IU/kg LPS or placebo as an intravenous bolus infusion. Outcome parameters were measured at baseline and 4h after LPS/placebo administration. At baseline and at 4h after administration a short period of 100% oxygen inhalation was used to assess retinal vasoreactivity to this stimulus. Perimacular white blood cell velocity, density and flux were assessed with the blue-field entoptic technique, retinal branch arterial and venous diameters were measured with a retinal vessel analyzer and red blood cell velocity in retinal branch veins was measured with laser Doppler velocimetry. LPS is associated with peripheral blood leukocytosis and increased white blood cell density in ocular microvessels (p<0.001). In addition, retinal arterial (p=0.02) and venous (p<0.01) diameters were increased. All retinal hemodynamic parameters showed a decrease during 100% oxygen breathing. This decrease was significantly blunted by LPS for all retinal outcome parameters except venous diameter (p=0.04 for white blood cell velocity, p=0.0002 for white blood cell density, p<0.0001 for white blood cell flux, p=0.01 for arterial diameter, p=0.02 for red blood cell velocity and p=0.006 for red blood cell flux). These data indicate that LPS-induced inflammation induces vascular dysregulation in the retina. This may provide a link between inflammation and vascular dysregulation. Further studies are warranted to investigate whether this model may be suitable to study inflammation induced vascular dysregulation in the eye.