 Piezoelectric biosensors are analytical devices that utilize the principle of affinity interactions to record changes in oscillation caused by a mass attached to a piezoelectric crystal. These sensors can be modified with antibodies, antigens, molecularly imprinted polymers, genetically encoded materials, and receptors for organic and biochemical compounds. Nanoparticles are often used as well, and applications of these sensors are discussed. The current state of research is summarized and the methods presented are evaluated. This article was authored by Miroslav Pohanka.