Organic nanowires self-assembled from small-molecule semiconductors and conducting polymers have attracted an enormous amount of interest for use in organic field-effect transistors. This new class of materials offers solution processability, the potential for elucidating transport mechanisms and structure-property relationships, and the realization of high-performance transistors that rival the performance of amorphous Si. We discuss the self-assembly of one-dimensional, single-crystalline organic nanowires, show the structures of commonly employed organic semiconductors, and review some of the advances in this field.