In the recent years, surface plasmon resonance (SPR) has become one of the major methods for studying and determination of biologically active materials exhibiting affinity interactions. SRP biosensors are increasingly used in biochemistry and bioanalytical chemistry to determine antibody-antigen interactions, to investigate DNA hybridization, to diagnose bacteria- and virus-induced diseases, to identify hormones, steroids, and immunoglobulins, to investigate blood plasma coagulation. Using SPR biosensors, it is possible to analyze the mixtures of substances with a very similar chemical structure because SPR allows identifying only those analytes that specifically interact with biologically active substance immobilized on the surface of SPR biosensor. SPR biosensors are applied to monitor interactions between immobilized biologically active substance and analyte in real-time without labeling. On the other hand, it is possible to investigate not only association of analyte with immobilized material, but also the dissociation of a newly formed complex. SPR biosensors in many cases may be used to perform up to 50 measurements with the same SPR chip with an immobilized biological recognition element. Therefore, at present SPR is one of the most promising methods for determining the interactions between ligand and receptor, antigen and antibody, thus being increasingly used in diagnostics and biomedical research.