An investigation of red blood cell interactions with contacting foreign surfaces is reported. The purpose of the study was to provide evidence to test the hypothesis that red cell membrane related deposit occurs when a suspension of red cells are exposed to a foreign surface. This membrane derived deposit is speculated to inhibit fibrinogen and albumin adsorption to glass and polyethylene (1,2). Experiments consisted of flowing suspensions of washed human red cells through a column packed with spherical glass beads. The column is then washed to remove suspended cells and eluted using a mild detergent solution. The red cells were observed to have retained their biconcave shape after passage through the column. The eluates are examined by UV-visible spectroscopy and SDS-PAGE, and are found to contain cell membrane components. It is therefore concluded that membrane material had been deposited on the bead surface. The SDS-PAGE data show that membrane skeleton proteins are missing from the eluate, while SEM examination indicates the presence of filamentous deposits on the bead surfaces. These data suggest that cell-surface interactions may occur through a tether-type mechanism involving extrusion of part of the red cell membrane. A 3 level, 3 factor fractional factorial design was used to quantitatively investigate the deposition in the column and to assess the effect of experimental variables on the phenomenon. The three factors studied were hematocrit, surface shear rate, and the presence of plasma in the suspending medium. Statistical analysis of the data generated indicates a positive correlation between hematocrit and the amount of surface deposit. However no correlation for the effects of shear rate or plasma content could be established In summary, red cell membrane components on contacting foreign surfaces were identified and a preliminary description of the phenomenon involved obtained. The deposit of membrane material is discussed in relation to Uniyal's "red cell effect" (1), and in the context of foreign surface induced thrombosis. It is hoped that this work will promote greater respect for the red cell as an important element in blood biomaterials interactions, and will prompt continued investigation on Uniyal's and other potential "red cell effects". / Thesis / Master of Engineering (ME)