This study was undertaken in order to investigate the use of fluid perfusion to prevent the adhesion of erythrocytes to a porous foreign surface. Three pore sizes each of two different commercially available polyethylene and aluminum oxide (AI2O3) tubes were investigated. Tubes were perfused with Ringer's solution while immersed in a bath of whole canine blood. Control tubes were prepared in an identical fashion but were not perfused. After testing, tubes were fixed in glutaraldehyde and dehydrated with graded ethanol. Samples were then sectioned and prepared for erythrocyte adhesion analysis by scanning electron microscopy (SEM). Results indicate that fluid perfusion can be used as a means to prevent erythrocyte adhesion in the range of pore sizes (10-60 micrometer diameter) studied. Critical values of the fluid perfusion rate are 0.027, 0.073 and 0.21 ml/min. cm2 for 10 micrometer, 35 micrometer, and 60 micrometer pore polyethylene respectively. The critical values for the ceramic samples are 0.22, 0.16 and 0.72 ml/min cm2 respectively for 7, 11 and 31 micrometer pore diameter respectively.