The prevalence of young-onset diabetes is rapidly rising in China. Young-onset diabetes is etiologically and phenotypically heterogeneous. Thirty percent to 50% of these patients have insulin secretory failure owing to autoimmune or monogenic or other yet to be identified forms of diabetes. Others have a strong family history of diabetes and exhibit features of the metabolic syndrome. Management of these young patients poses major diagnostic and therapeutic challenges, which require a multidisciplinary and holistic approach to ensure that these subjects are identified early and managed appropriately. Understanding the molecular basis of diabetes in these subjects may also eventually lead to improvement in diagnosis, classification, and treatment.