PDMAEMA (1-20μg/mL) exerted a concentration dependent proaggregant effect with a biphasic aggregation of washed platelets. This in vitro study highlighted that platelets display higher affinity for this polycation compared to red blood cells (RBCs), with an adsorption isotherm characteristics of a specific saturable binding site. To gain more insight into this polycation hemoreactivity, we followed the binding kinetics of a free form (FF) of fluorescein labelled PDMAEMA (below 15 kDa) in normal human blood using flow cytometry. As expected for other cationic carriers, intravenous administration of PDMAEMA can result in its ionic complexation with various negatively charged domains found within the blood. Poly(2-dimethylamino)ethyl methacrylate (PDMAEMA) is an attractive polycation frequently proposed as a non-viral vector for gene therapy.