Children born in Turku, Oulu and Tampere university cities in Finland are screened at birth for HLA alleles that carry increased risk to or protection from development of type 1 diabetes. Children carrying increased risk are followed at 3-12-month intervals for development of diabetes-associated autoantibodies. Children having at least two types of autoantibodies (of the four measured) in at least two consecutively drawn samples are randomized to receive daily intranasal insulin or placebo in a double-blinded 1:1 trial. Hypothesis is that intranasal insulin delays or prevents development of clinical type 1 diabetes. The primary outcome measure is development of clinical diabetes.