Abstract: Maternally inherited diabetes and deafness (MIDD) affects up to 1% of patients with diabetes but is often unrecognized by physicians. It is important to make an accurate genetic diagnosis, as there are implications for clinical investigation, diagnosis, management and genetic counselling. This review summarizes the range of clinical phenotypes associated with MIDD; outlines the advances in genetic diagnosis and pathogenesis of MIDD; summarizes the published prevalence data and provides guidance on the clinical management of these patients and their families.