The present report describes AIRE gene analysis in 25 children with autoimmune hepatitis type I or II. The heterozygous transversion c.961C > G (p.Ser278Arg) located in exon 7 was identified in 4 patients with autoimmune hepatitis type I, and mostly in those presenting with a positive family history for autoimmune diseases. In this subgroup of patients, the allelic frequency of this polymorphic variant was at least 3-fold higher than in healthy controls. These results suggest that heterozygous AIRE gene mutation may represent a genetic predisposition to childhood autoimmune hepatitis type I.