Organic electronics have, over the past two decades, developed into an exciting area of research and technology to replace classic inorganic semiconductors. Organic photovoltaics, light-emitting diodes, and thin-film transistors are already well developed and are currently being commercialized for a variety of applications. More recently, organic transistors have found new applications in the field of biosensors. The progress made in this direction is the topic of this review. Various configurations are presented, with their detection principle, and illustrated by examples from the literature.