More than 15 years ago glutaric aciduria type I has been included in newborn screening programmes and pilot studies evaluating the potential benefit of early diagnosis and start of metabolic treatment for patients with this disease have been initiated. At that time many important questions on epidemiology, diagnostic quality, natural history, treatment, and cost effectiveness were not sufficiently answered. In particular, it was rather unknown whether early treatment improves the outcome. After implementation of glutaric aciduria type I in an increasing number of countries, and with careful evaluation of disease course and impact of early treatment, there is now solid evidence that affected individuals do have substantial benefit and that newborn screening for this disease is a cost-effective diagnostic intervention. Despite this success, there are still limitations concerning diagnostic sensitivity for patients with a low excreting phenotype and knowledge on long-term disease outcome. In conclusion, it has become evident that tandem mass spectrometry-based newborn screening for glutaric aciduria type I is a powerful and cost-effective tool to prevent the manifestation of prognostically-relevant movement disorders in the majority of early diagnosed patients.