The aggregation and disaggregation behavior of erythrocytes reflects pathological states of the human body. The investigation of the aggregation and disaggregation process of human blood samples by laser spectroscopic measurements is described int he present paper. The whole blood samples were analyzed using a rotating coaxial cylinder system in combination with a special method for data processing. The erythrocyte aggregates were destroyed completely without injuring the cell membranes by shear forces arising during the cylinder rotation. The time behavior of the remission signal during the aggregation process was investigated. The disaggregation process was characterized by the dependence of the remission signal intensity on different applied shear rates.