Functional investigations using radionuclides to study protein adsorption and platelet adhesion onto biomaterials are described. The authors' novel methods use radiotracers with a dynamic technique. This allows direct observation of the interaction between blood, or simpler biological substances, and artificial materials. Several radiotracers were used in this study, including 111In-platelets, 123I-fibrinogen, 123I-antithrombin III, and 99mTc-tagged red blood cells. The detectors employed were a semiconductor diode or gamma-camera equipped with special collimators. The acquisition and treatment of data were performed with an original device. These methods allowed precise comparisons, especially between platelet adhesion upon different materials in the form of tubes and also protein adsorption and desorption. The results are discussed in terms of materials to be used for work in vivo.