Surface plasmon resonance is a method well-known for its sensibility to refractive index variations at a metal-dielectric interface. Surface plasmon imaging is an extension of this method. It allows the local study of refractive index variations resulting from interfacial modifications on a metallic surface. This technique is suitable to monitor in parallel, in real time and without any label hundreds of molecular interactions. The study of DNA:DNA hybridization is one of its applications.