An experimental analysis of the aggregates structure and their mobility under normal- and micro-g conditions is carried out. Fresh well mixed erythrocyte suspensions in plasma at 8.0% hematocrit are placed in a glass chamber and on-line video microscopic recording of the aggregation process under microgravity condition is carried out. The analysis of aggregate structure and mobility are carried out by an IBM-PC/AT based image processing system. The results show that (a) under normal gravity conditions the velocity of the formed aggregates depend on their sizes which tend to grow further by interacting with single cells and small aggregates, (b) under microgravity conditions the mobility of the aggregates reduces to zero and an alteration in their structural parameters is observed.