Type 1 diabetes is a common chronic disease in childhood and is increasing in incidence. Type 1 diabetes is diagnosed by hyperglycemia often in combination with symptoms of weight loss, thirst, fatigue and frequent urination, sometimes with ketoacidosis. The clinical onset is preceded by an asymptomatic phase identified by serum multiple beta-cell autoantibodies. Neonates and infants who are at increased risk to develop multiple beta-cell autoantibodies and type 1 diabetes can now be identified using genetic markers. This provides opportunity for introducing early therapies to prevent beta-cell autoimmunity and type 1 diabetes.