This lecture will deal with acoustic wave devices used in the sensing field. We will begin with a general description of SAW transducers principles. Then we will focus on a particular sensor which is known as one of the most sensitive: the Love-wave device. We will describe it from both a theoretical and experimental point of view: resolution of propagation equations in the multilayer structure, electrical characterisations, oscillator configuration. Sensing applications will be presented with a particular interest in chemical detection using sensors covered with a sensitive layer. We will study the mass-loading sensitivity and the influence of sensor parameters on it, and present results obtained in gas detection.