David Thorburn’s lab has acted as the main Australian referral centre for diagnosis of paediatric mitochondrial disease for nearly 30 years. He will describe the application of genomics, quantitative proteomics and other functional followup to retrospective cohorts of patients with Leigh syndrome, Complex I deficiency and a population-based cohort. The diagnostic yields in such cohorts are ~80%, compared to 40-50% yields in prospective cohorts, including in the Acute Care setting with turnaround times of less than 5 days. The ATAD3 locus will be described as an example of a genomic region that has been refractory to exome analysis, in which fusion genes generated by bialletic deletions and mono-allelic de novo duplications result in lethal perinatal mitochondrial disorders. The final topic to be discussed is the utility of prenatal diagnosis in a subset of women with a family history of mitochondrial DNA disease who are actually at low risk of having an affected child.