Acoustic sensor technologies have a long and prestigious history. However, liquid phase applications based upon thickness shear mode transducers are a relatively recent addition but are nonetheless being rapidly accepted as a broad usage analytical platform upon which to carry out label-free, real-time chemical, biological and pharmaceutical assays. This article discusses the development of thickness shear mode devices, current technologies, with a focus on the breadth of application and the future potential of the technique within the pharmaceutical and biochemical industries.