['To investigate the effects of endotoxin on adhesion of human red blood cells to human vascular endothelial cells under conditions of flow.', 'Prospective, randomized, controlled in vitro study.', 'University-affiliated cell biology laboratory.', 'Human erythrocytes and human vascular endothelial cells.', 'Fresh human erythrocytes and human vascular endothelial cells grown as monolayers were incubated with either saline or endotoxin. After incubation, endothelial monolayers were superfused with erythrocytes, and the number of erythrocytes adhering to the endothelial monolayer was quantified.', 'Adhesion of erythrocytes to vascular endothelium was measured under conditions of continuous flow in different settings: a) exposure of both endothelial cells and erythrocytes to saline; b) incubation of both erythrocytes and endothelial cells with endotoxin; c) exposure of erythrocytes only to endotoxin; d) incubation of endothelial cells only to endotoxin; and e) both the endothelial cells and erythrocytes incubated with different concentrations of endotoxin. Erythrocyte adhesion in the saline control group was 71 +/- 8 cells/mm2. Incubation of both components with endotoxin increased the number of adhesive erythrocytes to 172 +/- 9 cells/mm2 (p < .05). When only the endothelial cells were treated with endotoxin, 142 +/- 8 cells/mm2 adhered to the endothelial monolayer, whereas the incubation of the erythrocytes only to endotoxin resulted in adhesion of 102 +/- 3 cells/mm2. Decreasing concentrations of endotoxin reduced adhesion from 172 +/- 9 cells/mm2 (endotoxin, 75 microg/mL) to 165 +/- 9 cells/mm2 (endotoxin, 25 microg/mL), 153 +/- 4 cells/mm2 (endotoxin, 1 microg/mL), and 146 +/- 6.1 cells/mm2 (endotoxin, 5 ng/mL).'] Does endotoxin promote adhesion of human erythrocytes to human vascular endothelial cells under conditions of flow?