Mouse genetics has made crucial contributions to the understanding of the molecular mechanisms of hearing. With the help of a plethora of mouse mutants, many of the key genes that are involved in the development and functioning of the auditory system have been elucidated. Mouse mutants continue to shed light on the genetic and physiological bases of human hearing impairment, including both early- and late-onset deafness. A combination of genetic and physiological studies of mouse mutant lines, allied to investigations into the protein networks of the stereocilia bundle in the inner ear, are identifying key complexes that are crucial for auditory function and for providing profound insights into the underlying causes of hearing loss.