Transient expression of a type I interferon (IFN)-inducible gene signature is a risk factor for autoimmunity in children genetically predisposed to develop type 1 diabetes mellitus (T1DM). Microarray analysis was used to define a set of 225 IFN-inducible genes, the expression of which was quantified in 87 healthy controls, 64 individuals with T1DM and 109 children predisposed to develop T1DM IFN-inducible gene expression was found to precede autoantibody development in the latter group, but not in individuals with established disease.