This research proposes a thorough and systematic microrheological study of flow patterns and distributions of fluid velocity and wall shear stress in vessels which have undergone vascular reconstructive surgery in order to assess, from a fluid mechanical point of view, the adequacy of the basic anastomotic techniques currently used in vascular surgery, and to develop better methods which prevent or minimize the narrowing of vessels at sites of anastomoses. This will be achieved by performing various types of end-to-end and side-to-end anastomotic operations on dog femoral arteries with autologous artery and vein grafts, using conventional and modified techniques, harvesting the vessels several weeks or months after the operation, fixing and rendering them transparent and filming and analyzing the anatomical structure of the vessels and the behavior of tracer particles and hardened blood cells flowing through the vessels. The specific aims of the proposed research are: (1) to obtain precise and detailed flow patterns in regions of anastomoses in dog femoral arteries under normal (physiological) and altered flow conditions; (2) to acquire information on the distribution of fluid velocity and wall shear stress existing in the vicinity of anastomotic junctions in order to identify the regions of high and low shear; (3) to determine the specific feature of the geometric structure and flow patterns at sites of anastomoses; and (4) to correlate the results with the degree of narrowing of vessels causes by the formation of thrombi and the development of pseudointimal hyperplasia and atherosclerosis. The long term objectives of the proposed research are: (1) to arrive at a better understanding of the role of rheologic and geometric factors in the process of post-operative vascular occlusion at sites of anastomoses; and (2) to develop better anastomotic methods which prevent or minimize the narrowing and occlusion of vessels at such sites. The significance of the proposed research is that the method has, for the first time, been applied to vessels which have undergone surgical interventions in order to elucidate the role of rheologic and geometric factors in the genesis and development of thrombosis, pseudointimal hyperplasia and atherosclerosis at sites of vascular anastomoses. The results from the proposed research will provide essential and invaluable information to solve the problem at hand, which is not obtainable by any other existing means such as angiography and ultrasound Doppler techniques, nor with the highly sophisticated diagnostic techniques of CAT, PET and NMR.