The endothelial cell (EC) response during the first 2 h after traumatic hemorrhagic shock (THS) was analyzed in the rat mesentery by electron microscopy. Using a computer-assisted image analysis system, we interactively measured THS-induced changes of the area and the mean height of EC as well as the number of swollen EC occluding the capillary lumen. Analysis distinguished between capillaries presenting with the lumen blocked by corpuscular blood cells and capillaries with an open lumen. THS resulted in a significant increase in EC height of capillaries with an open lumen, but not of capillaries with lumen blocked by blood cells when compared with the control group (p < 0.05). This phenomenon was found to be most prominent 60 min after THS. In addition, THS was accompanied by a significantly increased number of swollen EC which occluded capillaries with an open lumen. From these results we conclude that swelling of EC contributes to THS-induced microvascular injury. Occlusion of the capillary lumen by EC swelling may be regarded as the morphological correlate of the THS-induced ‘no-reflow’ phenome