Maternally inherited diabetes and deafness (MIDD) is a rare form of diabetes, caused by a mutation in the mitochondrial DNA (mtDNA) which impairs mitochondrial function by decreasing the e ciency of the Leucine Transfer ribonucleic acid (tRNA) in adding amino acids to developing proteins. MIDD has a prevalence of 0.5-3% among diabetic population but almost always misdiagnosed and managed as either Type 1 or Type 2 diabetes mellitus, which adversely impacts their long term outcome. So it is important to differentiate these cases early enough and to institute correct treatment. We report on 3 cases of MIDD which was con rmed by genetic testing and ve of their rst degree relatives with similar clinical presentation. A heteroplasmic missense mutation in the MT-TL1 gene (chrm: 3243A > G mitochondrial DNA) was detected in all three patients but genetic con rmation was not possible in their relatives for want of patient consent for genetic study. To our knowledge, this is the largest series of MIDD reported from India.